22 files changed, 393 insertions, 160 deletions

diff --git a/core/src/async_runtime/executor.rs b/core/src/async_runtime/executor.rs
new file mode 100644
index 0000000..9335f12
--- /dev/null
+++ b/core/src/async_runtime/executor.rs
@@ -0,0 +1,100 @@
+use std::{future::Future, panic::catch_unwind, sync::Arc, thread};
+
+use once_cell::sync::OnceCell;
+
+#[cfg(feature = "smol")]
+pub use smol::Executor as SmolEx;
+
+#[cfg(feature = "tokio")]
+pub use tokio::runtime::Runtime;
+
+use super::Task;
+
+#[derive(Clone)]
+pub struct Executor {
+    #[cfg(feature = "smol")]
+    inner: Arc<SmolEx<'static>>,
+    #[cfg(feature = "tokio")]
+    inner: Arc<Runtime>,
+}
+
+impl Executor {
+    pub fn spawn<T: Send + 'static>(
+        &self,
+        future: impl Future<Output = T> + Send + 'static,
+    ) -> Task<T> {
+        self.inner.spawn(future).into()
+    }
+}
+
+static GLOBAL_EXECUTOR: OnceCell<Executor> = OnceCell::new();
+
+/// Returns a single-threaded global executor
+pub fn global_executor() -> Executor {
+    #[cfg(feature = "smol")]
+    fn init_executor() -> Executor {
+        let ex = smol::Executor::new();
+        thread::Builder::new()
+            .name("smol-executor".to_string())
+            .spawn(|| loop {
+                catch_unwind(|| {
+                    smol::block_on(global_executor().inner.run(std::future::pending::<()>()))
+                })
+                .ok();
+            })
+            .expect("cannot spawn executor thread");
+        // Prevent spawning another thread by running the process driver on this
+        // thread. see https://github.com/smol-rs/smol/blob/master/src/spawn.rs
+        ex.spawn(async_process::driver()).detach();
+        Executor {
+            inner: Arc::new(ex),
+        }
+    }
+
+    #[cfg(feature = "tokio")]
+    fn init_executor() -> Executor {
+        let ex = Arc::new(tokio::runtime::Runtime::new().expect("cannot build tokio runtime"));
+        let ex_cloned = ex.clone();
+        thread::Builder::new()
+            .name("tokio-executor".to_string())
+            .spawn(move || {
+                catch_unwind(|| ex_cloned.block_on(std::future::pending::<()>())).ok();
+            })
+            .expect("cannot spawn tokio runtime thread");
+        Executor { inner: ex }
+    }
+
+    GLOBAL_EXECUTOR.get_or_init(init_executor).clone()
+}
+
+#[cfg(feature = "smol")]
+impl From<Arc<smol::Executor<'static>>> for Executor {
+    fn from(ex: Arc<smol::Executor<'static>>) -> Executor {
+        Executor { inner: ex }
+    }
+}
+
+#[cfg(feature = "tokio")]
+impl From<Arc<tokio::runtime::Runtime>> for Executor {
+    fn from(rt: Arc<tokio::runtime::Runtime>) -> Executor {
+        Executor { inner: rt }
+    }
+}
+
+#[cfg(feature = "smol")]
+impl From<smol::Executor<'static>> for Executor {
+    fn from(ex: smol::Executor<'static>) -> Executor {
+        Executor {
+            inner: Arc::new(ex),
+        }
+    }
+}
+
+#[cfg(feature = "tokio")]
+impl From<tokio::runtime::Runtime> for Executor {
+    fn from(rt: tokio::runtime::Runtime) -> Executor {
+        Executor {
+            inner: Arc::new(rt),
+        }
+    }
+}
diff --git a/core/src/async_runtime/io.rs b/core/src/async_runtime/io.rs
new file mode 100644
index 0000000..161c258
--- /dev/null
+++ b/core/src/async_runtime/io.rs
@@ -0,0 +1,9 @@
+#[cfg(feature = "smol")]
+pub use smol::io::{
+    split, AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt, ReadHalf, WriteHalf,
+};
+
+#[cfg(feature = "tokio")]
+pub use tokio::io::{
+    split, AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt, ReadHalf, WriteHalf,
+};
diff --git a/core/src/async_runtime/lock.rs b/core/src/async_runtime/lock.rs
new file mode 100644
index 0000000..fc84d1d
--- /dev/null
+++ b/core/src/async_runtime/lock.rs
@@ -0,0 +1,5 @@
+#[cfg(feature = "smol")]
+pub use smol::lock::{Mutex, MutexGuard, OnceCell, RwLock};
+
+#[cfg(feature = "tokio")]
+pub use tokio::sync::{Mutex, MutexGuard, OnceCell, RwLock};
diff --git a/core/src/async_runtime/mod.rs b/core/src/async_runtime/mod.rs
new file mode 100644
index 0000000..d91d01b
--- /dev/null
+++ b/core/src/async_runtime/mod.rs
@@ -0,0 +1,25 @@
+mod executor;
+pub mod io;
+pub mod lock;
+pub mod net;
+mod spawn;
+mod task;
+mod timer;
+
+pub use executor::{global_executor, Executor};
+pub use spawn::spawn;
+pub use task::Task;
+
+#[cfg(test)]
+pub fn block_on<T>(future: impl std::future::Future<Output = T>) -> T {
+    #[cfg(feature = "smol")]
+    let result = smol::block_on(future);
+    #[cfg(feature = "tokio")]
+    let result = tokio::runtime::Builder::new_current_thread()
+        .enable_all()
+        .build()
+        .unwrap()
+        .block_on(future);
+
+    result
+}
diff --git a/core/src/async_runtime/net.rs b/core/src/async_runtime/net.rs
new file mode 100644
index 0000000..5c004ce
--- /dev/null
+++ b/core/src/async_runtime/net.rs
@@ -0,0 +1,12 @@
+pub use std::os::unix::net::SocketAddr;
+
+#[cfg(feature = "smol")]
+pub use smol::net::{
+    unix::{SocketAddr as UnixSocketAddr, UnixListener, UnixStream},
+    TcpListener, TcpStream, UdpSocket,
+};
+
+#[cfg(feature = "tokio")]
+pub use tokio::net::{
+    unix::SocketAddr as UnixSocketAddr, TcpListener, TcpStream, UdpSocket, UnixListener, UnixStream,
+};
diff --git a/core/src/async_runtime/spawn.rs b/core/src/async_runtime/spawn.rs
new file mode 100644
index 0000000..2760982
--- /dev/null
+++ b/core/src/async_runtime/spawn.rs
@@ -0,0 +1,12 @@
+use std::future::Future;
+
+use super::Task;
+
+pub fn spawn<T: Send + 'static>(future: impl Future<Output = T> + Send + 'static) -> Task<T> {
+    #[cfg(feature = "smol")]
+    let result: Task<T> = smol::spawn(future).into();
+    #[cfg(feature = "tokio")]
+    let result: Task<T> = tokio::spawn(future).into();
+
+    result
+}
diff --git a/core/src/async_runtime/task.rs b/core/src/async_runtime/task.rs
new file mode 100644
index 0000000..a681b0f
--- /dev/null
+++ b/core/src/async_runtime/task.rs
@@ -0,0 +1,52 @@
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+use crate::error::Error;
+
+pub struct Task<T> {
+    #[cfg(feature = "smol")]
+    inner_task: smol::Task<T>,
+    #[cfg(feature = "tokio")]
+    inner_task: tokio::task::JoinHandle<T>,
+}
+
+impl<T> Task<T> {
+    pub async fn cancel(self) {
+        #[cfg(feature = "smol")]
+        self.inner_task.cancel().await;
+        #[cfg(feature = "tokio")]
+        self.inner_task.abort();
+    }
+}
+
+impl<T> Future for Task<T> {
+    type Output = Result<T, Error>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        #[cfg(feature = "smol")]
+        let result = smol::Task::poll(Pin::new(&mut self.inner_task), cx);
+        #[cfg(feature = "tokio")]
+        let result = tokio::task::JoinHandle::poll(Pin::new(&mut self.inner_task), cx);
+
+        #[cfg(feature = "smol")]
+        return result.map(Ok);
+
+        #[cfg(feature = "tokio")]
+        return result.map_err(|e| e.into());
+    }
+}
+
+#[cfg(feature = "smol")]
+impl<T> From<smol::Task<T>> for Task<T> {
+    fn from(t: smol::Task<T>) -> Task<T> {
+        Task { inner_task: t }
+    }
+}
+
+#[cfg(feature = "tokio")]
+impl<T> From<tokio::task::JoinHandle<T>> for Task<T> {
+    fn from(t: tokio::task::JoinHandle<T>) -> Task<T> {
+        Task { inner_task: t }
+    }
+}
diff --git a/core/src/async_runtime/timer.rs b/core/src/async_runtime/timer.rs
new file mode 100644
index 0000000..8b13789
--- /dev/null
+++ b/core/src/async_runtime/timer.rs
@@ -0,0 +1 @@
+
diff --git a/core/src/async_util/backoff.rs b/core/src/async_util/backoff.rs
index 4a0ab35..70e63b3 100644
--- a/core/src/async_util/backoff.rs
+++ b/core/src/async_util/backoff.rs
@@ -4,7 +4,7 @@ use std::{
     time::Duration,
 };
 
-use smol::Timer;
+use super::sleep;
 
 /// Exponential backoff
 /// <https://en.wikipedia.org/wiki/Exponential_backoff>
@@ -57,7 +57,7 @@ impl Backoff {
     /// Retruns the delay value.
     pub async fn sleep(&self) -> u64 {
         if self.stop.load(Ordering::SeqCst) {
-            Timer::after(Duration::from_millis(self.max_delay)).await;
+            sleep(Duration::from_millis(self.max_delay)).await;
             return self.max_delay;
         }
 
@@ -71,7 +71,7 @@ impl Backoff {
 
         self.retries.store(retries + 1, Ordering::SeqCst);
 
-        Timer::after(Duration::from_millis(delay)).await;
+        sleep(Duration::from_millis(delay)).await;
         delay
     }
 
@@ -84,15 +84,18 @@ impl Backoff {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use std::sync::Arc;
 
+    use crate::async_runtime::{block_on, spawn};
+
+    use super::*;
+
     #[test]
     fn test_backoff() {
-        smol::block_on(async move {
+        block_on(async move {
             let backoff = Arc::new(Backoff::new(5, 15));
             let backoff_c = backoff.clone();
-            smol::spawn(async move {
+            spawn(async move {
                 let delay = backoff_c.sleep().await;
                 assert_eq!(delay, 5);
 
@@ -102,14 +105,16 @@ mod tests {
                 let delay = backoff_c.sleep().await;
                 assert_eq!(delay, 15);
             })
-            .await;
+            .await
+            .unwrap();
 
-            smol::spawn(async move {
+            spawn(async move {
                 backoff.reset();
                 let delay = backoff.sleep().await;
                 assert_eq!(delay, 5);
             })
-            .await;
+            .await
+            .unwrap();
         });
     }
 }
diff --git a/core/src/async_util/condvar.rs b/core/src/async_util/condvar.rs
index d3bc15b..c3f373d 100644
--- a/core/src/async_util/condvar.rs
+++ b/core/src/async_util/condvar.rs
@@ -6,9 +6,7 @@ use std::{
     task::{Context, Poll, Waker},
 };
 
-use smol::lock::MutexGuard;
-
-use crate::util::random_16;
+use crate::{async_runtime::lock::MutexGuard, util::random_16};
 
 /// CondVar is an async version of <https://doc.rust-lang.org/std/sync/struct.Condvar.html>
 ///
@@ -17,9 +15,8 @@ use crate::util::random_16;
 ///```
 /// use std::sync::Arc;
 ///
-/// use smol::lock::Mutex;
-///
 /// use karyon_core::async_util::CondVar;
+/// use karyon_core::async_runtime::{spawn, lock::Mutex};
 ///
 ///  async {
 ///     
@@ -28,7 +25,7 @@ use crate::util::random_16;
 ///
 ///     let val_cloned = val.clone();
 ///     let condvar_cloned = condvar.clone();
-///     smol::spawn(async move {
+///     spawn(async move {
 ///         let mut val = val_cloned.lock().await;
 ///
 ///         // While the boolean flag is false, wait for a signal.
@@ -40,7 +37,7 @@ use crate::util::random_16;
 ///     });
 ///
 ///     let condvar_cloned = condvar.clone();
-///     smol::spawn(async move {
+///     spawn(async move {
 ///         let mut val = val.lock().await;
 ///
 ///         // While the boolean flag is false, wait for a signal.
@@ -71,7 +68,10 @@ impl CondVar {
 
     /// Blocks the current task until this condition variable receives a notification.
     pub async fn wait<'a, T>(&self, g: MutexGuard<'a, T>) -> MutexGuard<'a, T> {
+        #[cfg(feature = "smol")]
         let m = MutexGuard::source(&g);
+        #[cfg(feature = "tokio")]
+        let m = MutexGuard::mutex(&g);
 
         CondVarAwait::new(self, g).await;
 
@@ -206,8 +206,6 @@ impl Wakers {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
-    use smol::lock::Mutex;
     use std::{
         collections::VecDeque,
         sync::{
@@ -216,6 +214,10 @@ mod tests {
         },
     };
 
+    use crate::async_runtime::{block_on, lock::Mutex, spawn};
+
+    use super::*;
+
     // The tests below demonstrate a solution to a problem in the Wikipedia
     // explanation of condition variables:
     // https://en.wikipedia.org/wiki/Monitor_(synchronization)#Solving_the_bounded_producer/consumer_problem.
@@ -243,7 +245,7 @@ mod tests {
 
     #[test]
     fn test_condvar_signal() {
-        smol::block_on(async {
+        block_on(async {
             let number_of_tasks = 30;
 
             let queue = Arc::new(Mutex::new(Queue::new(5)));
@@ -254,7 +256,7 @@ mod tests {
             let condvar_full_cloned = condvar_full.clone();
             let condvar_empty_cloned = condvar_empty.clone();
 
-            let _producer1 = smol::spawn(async move {
+            let _producer1 = spawn(async move {
                 for i in 1..number_of_tasks {
                     // Lock queue mtuex
                     let mut queue = queue_cloned.lock().await;
@@ -275,7 +277,7 @@ mod tests {
             let queue_cloned = queue.clone();
             let task_consumed = Arc::new(AtomicUsize::new(0));
             let task_consumed_ = task_consumed.clone();
-            let consumer = smol::spawn(async move {
+            let consumer = spawn(async move {
                 for _ in 1..number_of_tasks {
                     // Lock queue mtuex
                     let mut queue = queue_cloned.lock().await;
@@ -297,7 +299,7 @@ mod tests {
                 }
             });
 
-            consumer.await;
+            let _ = consumer.await;
             assert!(queue.lock().await.is_empty());
             assert_eq!(task_consumed.load(Ordering::Relaxed), 29);
         });
@@ -305,7 +307,7 @@ mod tests {
 
     #[test]
     fn test_condvar_broadcast() {
-        smol::block_on(async {
+        block_on(async {
             let tasks = 30;
 
             let queue = Arc::new(Mutex::new(Queue::new(5)));
@@ -313,7 +315,7 @@ mod tests {
 
             let queue_cloned = queue.clone();
             let condvar_cloned = condvar.clone();
-            let _producer1 = smol::spawn(async move {
+            let _producer1 = spawn(async move {
                 for i in 1..tasks {
                     // Lock queue mtuex
                     let mut queue = queue_cloned.lock().await;
@@ -333,7 +335,7 @@ mod tests {
 
             let queue_cloned = queue.clone();
             let condvar_cloned = condvar.clone();
-            let _producer2 = smol::spawn(async move {
+            let _producer2 = spawn(async move {
                 for i in 1..tasks {
                     // Lock queue mtuex
                     let mut queue = queue_cloned.lock().await;
@@ -355,7 +357,7 @@ mod tests {
             let task_consumed = Arc::new(AtomicUsize::new(0));
             let task_consumed_ = task_consumed.clone();
 
-            let consumer = smol::spawn(async move {
+            let consumer = spawn(async move {
                 for _ in 1..((tasks * 2) - 1) {
                     {
                         // Lock queue mutex
@@ -379,7 +381,7 @@ mod tests {
                 }
             });
 
-            consumer.await;
+            let _ = consumer.await;
             assert!(queue.lock().await.is_empty());
             assert_eq!(task_consumed.load(Ordering::Relaxed), 58);
         });
diff --git a/core/src/async_util/condwait.rs b/core/src/async_util/condwait.rs
index 6aa8a3c..76c6a05 100644
--- a/core/src/async_util/condwait.rs
+++ b/core/src/async_util/condwait.rs
@@ -1,6 +1,5 @@
-use smol::lock::Mutex;
-
 use super::CondVar;
+use crate::async_runtime::lock::Mutex;
 
 /// CondWait is a wrapper struct for CondVar with a Mutex boolean flag.
 ///
@@ -10,11 +9,12 @@ use super::CondVar;
 /// use std::sync::Arc;
 ///
 /// use karyon_core::async_util::CondWait;
+/// use karyon_core::async_runtime::spawn;
 ///
 ///  async {
 ///     let cond_wait = Arc::new(CondWait::new());
 ///     let cond_wait_cloned = cond_wait.clone();
-///     let task = smol::spawn(async move {
+///     let task = spawn(async move {
 ///         cond_wait_cloned.wait().await;
 ///         // ...
 ///     });
@@ -76,21 +76,24 @@ impl Default for CondWait {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use std::sync::{
         atomic::{AtomicUsize, Ordering},
         Arc,
     };
 
+    use crate::async_runtime::{block_on, spawn};
+
+    use super::*;
+
     #[test]
     fn test_cond_wait() {
-        smol::block_on(async {
+        block_on(async {
             let cond_wait = Arc::new(CondWait::new());
             let count = Arc::new(AtomicUsize::new(0));
 
             let cond_wait_cloned = cond_wait.clone();
             let count_cloned = count.clone();
-            let task = smol::spawn(async move {
+            let task = spawn(async move {
                 cond_wait_cloned.wait().await;
                 count_cloned.fetch_add(1, Ordering::Relaxed);
                 // do something
@@ -99,7 +102,7 @@ mod tests {
             // Send a signal to the waiting task
             cond_wait.signal().await;
 
-            task.await;
+            let _ = task.await;
 
             // Reset the boolean flag
             cond_wait.reset().await;
@@ -108,7 +111,7 @@ mod tests {
 
             let cond_wait_cloned = cond_wait.clone();
             let count_cloned = count.clone();
-            let task1 = smol::spawn(async move {
+            let task1 = spawn(async move {
                 cond_wait_cloned.wait().await;
                 count_cloned.fetch_add(1, Ordering::Relaxed);
                 // do something
@@ -116,7 +119,7 @@ mod tests {
 
             let cond_wait_cloned = cond_wait.clone();
             let count_cloned = count.clone();
-            let task2 = smol::spawn(async move {
+            let task2 = spawn(async move {
                 cond_wait_cloned.wait().await;
                 count_cloned.fetch_add(1, Ordering::Relaxed);
                 // do something
@@ -125,8 +128,8 @@ mod tests {
             // Broadcast a signal to all waiting tasks
             cond_wait.broadcast().await;
 
-            task1.await;
-            task2.await;
+            let _ = task1.await;
+            let _ = task2.await;
             assert_eq!(count.load(Ordering::Relaxed), 3);
         });
     }
diff --git a/core/src/async_util/executor.rs b/core/src/async_util/executor.rs
deleted file mode 100644
index 3e7aa06..0000000
--- a/core/src/async_util/executor.rs
+++ /dev/null
@@ -1,30 +0,0 @@
-use std::{panic::catch_unwind, sync::Arc, thread};
-
-use async_lock::OnceCell;
-use smol::Executor as SmolEx;
-
-static GLOBAL_EXECUTOR: OnceCell<Arc<smol::Executor<'_>>> = OnceCell::new();
-
-/// A pointer to an Executor
-pub type Executor<'a> = Arc<SmolEx<'a>>;
-
-/// Returns a single-threaded global executor
-pub(crate) fn global_executor() -> Executor<'static> {
-    fn init_executor() -> Executor<'static> {
-        let ex = smol::Executor::new();
-        thread::Builder::new()
-            .spawn(|| loop {
-                catch_unwind(|| {
-                    smol::block_on(global_executor().run(smol::future::pending::<()>()))
-                })
-                .ok();
-            })
-            .expect("cannot spawn executor thread");
-        // Prevent spawning another thread by running the process driver on this
-        // thread. see https://github.com/smol-rs/smol/blob/master/src/spawn.rs
-        ex.spawn(async_process::driver()).detach();
-        Arc::new(ex)
-    }
-
-    GLOBAL_EXECUTOR.get_or_init_blocking(init_executor).clone()
-}
diff --git a/core/src/async_util/mod.rs b/core/src/async_util/mod.rs
index 2916118..54b9607 100644
--- a/core/src/async_util/mod.rs
+++ b/core/src/async_util/mod.rs
@@ -1,15 +1,15 @@
 mod backoff;
 mod condvar;
 mod condwait;
-mod executor;
 mod select;
+mod sleep;
 mod task_group;
 mod timeout;
 
 pub use backoff::Backoff;
 pub use condvar::CondVar;
 pub use condwait::CondWait;
-pub use executor::Executor;
 pub use select::{select, Either};
+pub use sleep::sleep;
 pub use task_group::{TaskGroup, TaskResult};
 pub use timeout::timeout;
diff --git a/core/src/async_util/select.rs b/core/src/async_util/select.rs
index 0977fa9..2008cb5 100644
--- a/core/src/async_util/select.rs
+++ b/core/src/async_util/select.rs
@@ -1,8 +1,8 @@
+use std::future::Future;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 
 use pin_project_lite::pin_project;
-use smol::future::Future;
 
 /// Returns the result of the future that completes first, preferring future1
 /// if both are ready.
@@ -75,14 +75,16 @@ where
 
 #[cfg(test)]
 mod tests {
-    use super::{select, Either};
-    use smol::Timer;
     use std::future;
 
+    use crate::{async_runtime::block_on, async_util::sleep};
+
+    use super::{select, Either};
+
     #[test]
     fn test_async_select() {
-        smol::block_on(async move {
-            let fut = select(Timer::never(), future::ready(0 as u32)).await;
+        block_on(async move {
+            let fut = select(sleep(std::time::Duration::MAX), future::ready(0 as u32)).await;
             assert!(matches!(fut, Either::Right(0)));
 
             let fut1 = future::pending::<String>();
diff --git a/core/src/async_util/sleep.rs b/core/src/async_util/sleep.rs
new file mode 100644
index 0000000..f72b825
--- /dev/null
+++ b/core/src/async_util/sleep.rs
@@ -0,0 +1,6 @@
+pub async fn sleep(duration: std::time::Duration) {
+    #[cfg(feature = "smol")]
+    smol::Timer::after(duration).await;
+    #[cfg(feature = "tokio")]
+    tokio::time::sleep(duration).await;
+}
diff --git a/core/src/async_util/task_group.rs b/core/src/async_util/task_group.rs
index 7f05696..5af75ed 100644
--- a/core/src/async_util/task_group.rs
+++ b/core/src/async_util/task_group.rs
@@ -1,8 +1,8 @@
 use std::{future::Future, sync::Arc, sync::Mutex};
 
-use async_task::FallibleTask;
+use crate::async_runtime::{global_executor, Executor, Task};
 
-use super::{executor::global_executor, select, CondWait, Either, Executor};
+use super::{select, CondWait, Either};
 
 /// TaskGroup A group that contains spawned tasks.
 ///
@@ -12,28 +12,25 @@ use super::{executor::global_executor, select, CondWait, Either, Executor};
 ///
 /// use std::sync::Arc;
 ///
-/// use karyon_core::async_util::TaskGroup;
+/// use karyon_core::async_util::{TaskGroup, sleep};
 ///
 /// async {
+///     let group = TaskGroup::new();
 ///
-///     let ex = Arc::new(smol::Executor::new());
-///     let group = TaskGroup::with_executor(ex);
-///
-///     group.spawn(smol::Timer::never(), |_| async {});
+///     group.spawn(sleep(std::time::Duration::MAX), |_| async {});
 ///
 ///     group.cancel().await;
 ///
 /// };
 ///
 /// ```
-///
-pub struct TaskGroup<'a> {
+pub struct TaskGroup {
     tasks: Mutex<Vec<TaskHandler>>,
     stop_signal: Arc<CondWait>,
-    executor: Executor<'a>,
+    executor: Executor,
 }
 
-impl TaskGroup<'static> {
+impl TaskGroup {
     /// Creates a new TaskGroup without providing an executor
     ///
     /// This will spawn a task onto a global executor (single-threaded by default).
@@ -44,11 +41,9 @@ impl TaskGroup<'static> {
             executor: global_executor(),
         }
     }
-}
 
-impl<'a> TaskGroup<'a> {
     /// Creates a new TaskGroup by providing an executor
-    pub fn with_executor(executor: Executor<'a>) -> Self {
+    pub fn with_executor(executor: Executor) -> Self {
         Self {
             tasks: Mutex::new(Vec::new()),
             stop_signal: Arc::new(CondWait::new()),
@@ -61,10 +56,10 @@ impl<'a> TaskGroup<'a> {
     /// parameter, indicating whether the task completed or was canceled.
     pub fn spawn<T, Fut, CallbackF, CallbackFut>(&self, fut: Fut, callback: CallbackF)
     where
-        T: Send + Sync + 'a,
-        Fut: Future<Output = T> + Send + 'a,
-        CallbackF: FnOnce(TaskResult<T>) -> CallbackFut + Send + 'a,
-        CallbackFut: Future<Output = ()> + Send + 'a,
+        T: Send + Sync + 'static,
+        Fut: Future<Output = T> + Send + 'static,
+        CallbackF: FnOnce(TaskResult<T>) -> CallbackFut + Send + 'static,
+        CallbackFut: Future<Output = ()> + Send + 'static,
     {
         let task = TaskHandler::new(
             self.executor.clone(),
@@ -100,7 +95,7 @@ impl<'a> TaskGroup<'a> {
     }
 }
 
-impl Default for TaskGroup<'static> {
+impl Default for TaskGroup {
     fn default() -> Self {
         Self::new()
     }
@@ -124,42 +119,40 @@ impl<T: std::fmt::Debug> std::fmt::Display for TaskResult<T> {
 
 /// TaskHandler
 pub struct TaskHandler {
-    task: FallibleTask<()>,
+    task: Task<()>,
     cancel_flag: Arc<CondWait>,
 }
 
 impl<'a> TaskHandler {
     /// Creates a new task handler
     fn new<T, Fut, CallbackF, CallbackFut>(
-        ex: Executor<'a>,
+        ex: Executor,
         fut: Fut,
         callback: CallbackF,
         stop_signal: Arc<CondWait>,
     ) -> TaskHandler
     where
-        T: Send + Sync + 'a,
-        Fut: Future<Output = T> + Send + 'a,
-        CallbackF: FnOnce(TaskResult<T>) -> CallbackFut + Send + 'a,
-        CallbackFut: Future<Output = ()> + Send + 'a,
+        T: Send + Sync + 'static,
+        Fut: Future<Output = T> + Send + 'static,
+        CallbackF: FnOnce(TaskResult<T>) -> CallbackFut + Send + 'static,
+        CallbackFut: Future<Output = ()> + Send + 'static,
     {
         let cancel_flag = Arc::new(CondWait::new());
         let cancel_flag_c = cancel_flag.clone();
-        let task = ex
-            .spawn(async move {
-                // Waits for either the stop signal or the task to complete.
-                let result = select(stop_signal.wait(), fut).await;
+        let task = ex.spawn(async move {
+            // Waits for either the stop signal or the task to complete.
+            let result = select(stop_signal.wait(), fut).await;
 
-                let result = match result {
-                    Either::Left(_) => TaskResult::Cancelled,
-                    Either::Right(res) => TaskResult::Completed(res),
-                };
+            let result = match result {
+                Either::Left(_) => TaskResult::Cancelled,
+                Either::Right(res) => TaskResult::Completed(res),
+            };
 
-                // Call the callback
-                callback(result).await;
+            // Call the callback
+            callback(result).await;
 
-                cancel_flag_c.signal().await;
-            })
-            .fallible();
+            cancel_flag_c.signal().await;
+        });
 
         TaskHandler { task, cancel_flag }
     }
@@ -173,14 +166,52 @@ impl<'a> TaskHandler {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use std::{future, sync::Arc};
 
+    use crate::async_runtime::block_on;
+    use crate::async_util::sleep;
+
+    use super::*;
+
+    #[cfg(feature = "tokio")]
+    #[test]
+    fn test_task_group_with_tokio_executor() {
+        let ex = Arc::new(tokio::runtime::Runtime::new().unwrap());
+        ex.clone().block_on(async move {
+            let group = Arc::new(TaskGroup::with_executor(ex.into()));
+
+            group.spawn(future::ready(0), |res| async move {
+                assert!(matches!(res, TaskResult::Completed(0)));
+            });
+
+            group.spawn(future::pending::<()>(), |res| async move {
+                assert!(matches!(res, TaskResult::Cancelled));
+            });
+
+            let groupc = group.clone();
+            group.spawn(
+                async move {
+                    groupc.spawn(future::pending::<()>(), |res| async move {
+                        assert!(matches!(res, TaskResult::Cancelled));
+                    });
+                },
+                |res| async move {
+                    assert!(matches!(res, TaskResult::Completed(_)));
+                },
+            );
+
+            // Do something
+            tokio::time::sleep(std::time::Duration::from_millis(50)).await;
+            group.cancel().await;
+        });
+    }
+
+    #[cfg(feature = "smol")]
     #[test]
-    fn test_task_group_with_executor() {
+    fn test_task_group_with_smol_executor() {
         let ex = Arc::new(smol::Executor::new());
         smol::block_on(ex.clone().run(async move {
-            let group = Arc::new(TaskGroup::with_executor(ex));
+            let group = Arc::new(TaskGroup::with_executor(ex.into()));
 
             group.spawn(future::ready(0), |res| async move {
                 assert!(matches!(res, TaskResult::Completed(0)));
@@ -210,7 +241,7 @@ mod tests {
 
     #[test]
     fn test_task_group() {
-        smol::block_on(async {
+        block_on(async {
             let group = Arc::new(TaskGroup::new());
 
             group.spawn(future::ready(0), |res| async move {
@@ -234,7 +265,7 @@ mod tests {
             );
 
             // Do something
-            smol::Timer::after(std::time::Duration::from_millis(50)).await;
+            sleep(std::time::Duration::from_millis(50)).await;
             group.cancel().await;
         });
     }
diff --git a/core/src/async_util/timeout.rs b/core/src/async_util/timeout.rs
index cf3c490..9ac64c8 100644
--- a/core/src/async_util/timeout.rs
+++ b/core/src/async_util/timeout.rs
@@ -1,10 +1,9 @@
 use std::{future::Future, time::Duration};
 
-use smol::Timer;
-
-use super::{select, Either};
 use crate::{error::Error, Result};
 
+use super::{select, sleep, Either};
+
 /// Waits for a future to complete or times out if it exceeds a specified
 /// duration.
 ///
@@ -26,7 +25,7 @@ pub async fn timeout<T, F>(delay: Duration, future1: F) -> Result<T>
 where
     F: Future<Output = T>,
 {
-    let result = select(Timer::after(delay), future1).await;
+    let result = select(sleep(delay), future1).await;
 
     match result {
         Either::Left(_) => Err(Error::Timeout),
@@ -41,11 +40,11 @@ mod tests {
 
     #[test]
     fn test_timeout() {
-        smol::block_on(async move {
+        crate::async_runtime::block_on(async move {
             let fut = future::pending::<()>();
             assert!(timeout(Duration::from_millis(10), fut).await.is_err());
 
-            let fut = smol::Timer::after(Duration::from_millis(10));
+            let fut = sleep(Duration::from_millis(10));
             assert!(timeout(Duration::from_millis(50), fut).await.is_ok())
         });
     }
diff --git a/core/src/error.rs b/core/src/error.rs
index cc60696..2b8f641 100644
--- a/core/src/error.rs
+++ b/core/src/error.rs
@@ -20,11 +20,15 @@ pub enum Error {
     #[error(transparent)]
     Ed25519(#[from] ed25519_dalek::ed25519::Error),
 
+    #[cfg(feature = "tokio")]
+    #[error(transparent)]
+    TokioJoinError(#[from] tokio::task::JoinError),
+
     #[error("Channel Send Error: {0}")]
     ChannelSend(String),
 
     #[error(transparent)]
-    ChannelRecv(#[from] smol::channel::RecvError),
+    ChannelRecv(#[from] async_channel::RecvError),
 
     #[error(transparent)]
     BincodeDecode(#[from] bincode::error::DecodeError),
@@ -33,8 +37,8 @@ pub enum Error {
     BincodeEncode(#[from] bincode::error::EncodeError),
 }
 
-impl<T> From<smol::channel::SendError<T>> for Error {
-    fn from(error: smol::channel::SendError<T>) -> Self {
+impl<T> From<async_channel::SendError<T>> for Error {
+    fn from(error: async_channel::SendError<T>) -> Self {
         Error::ChannelSend(error.to_string())
     }
 }
diff --git a/core/src/event.rs b/core/src/event.rs
index ef40205..e8692ef 100644
--- a/core/src/event.rs
+++ b/core/src/event.rs
@@ -5,14 +5,11 @@ use std::{
     sync::{Arc, Weak},
 };
 
+use async_channel::{Receiver, Sender};
 use chrono::{DateTime, Utc};
 use log::{error, trace};
-use smol::{
-    channel::{Receiver, Sender},
-    lock::Mutex,
-};
 
-use crate::{util::random_16, Result};
+use crate::{async_runtime::lock::Mutex, util::random_16, Result};
 
 pub type ArcEventSys<T> = Arc<EventSys<T>>;
 pub type WeakEventSys<T> = Weak<EventSys<T>>;
@@ -139,7 +136,7 @@ where
         self: &Arc<Self>,
         topic: &T,
     ) -> EventListener<T, E> {
-        let chan = smol::channel::unbounded();
+        let chan = async_channel::unbounded();
 
         let topics = &mut self.listeners.lock().await;
 
@@ -310,6 +307,8 @@ pub trait EventValueTopic: EventValueAny + EventValue {
 
 #[cfg(test)]
 mod tests {
+    use crate::async_runtime::block_on;
+
     use super::*;
 
     #[derive(Hash, PartialEq, Eq, Debug, Clone)]
@@ -337,11 +336,6 @@ mod tests {
     }
 
     #[derive(Clone, Debug, PartialEq)]
-    struct D {
-        d_value: usize,
-    }
-
-    #[derive(Clone, Debug, PartialEq)]
     struct E {
         e_value: usize,
     }
@@ -369,12 +363,6 @@ mod tests {
         }
     }
 
-    impl EventValue for D {
-        fn id() -> &'static str {
-            "D"
-        }
-    }
-
     impl EventValue for E {
         fn id() -> &'static str {
             "E"
@@ -396,7 +384,7 @@ mod tests {
 
     #[test]
     fn test_event_sys() {
-        smol::block_on(async move {
+        block_on(async move {
             let event_sys = EventSys::<Topic>::new();
 
             let a_listener = event_sys.register::<A>(&Topic::TopicA).await;
diff --git a/core/src/lib.rs b/core/src/lib.rs
index ae88188..62052a8 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -1,8 +1,13 @@
+#[cfg(all(feature = "smol", feature = "tokio"))]
+compile_error!("Only one async runtime feature should be enabled");
+
+#[cfg(not(any(feature = "smol", feature = "tokio")))]
+compile_error!("At least one async runtime feature must be enabled for this crate.");
+
 /// A set of helper tools and functions.
 pub mod util;
 
-/// A module containing async utilities that work with the
-/// [`smol`](https://github.com/smol-rs/smol) async runtime.
+/// A set of async utilities.
 pub mod async_util;
 
 /// Represents karyon's Core Error.
@@ -14,8 +19,12 @@ pub mod event;
 /// A simple publish-subscribe system [`Read More`](./pubsub/struct.Publisher.html)
 pub mod pubsub;
 
+/// A cross-compatible async runtime
+pub mod async_runtime;
+
 #[cfg(feature = "crypto")]
+
 /// Collects common cryptographic tools
 pub mod crypto;
 
-use error::Result;
+pub use error::{Error, Result};
diff --git a/core/src/pubsub.rs b/core/src/pubsub.rs
index f5cb69b..bcc24ef 100644
--- a/core/src/pubsub.rs
+++ b/core/src/pubsub.rs
@@ -1,9 +1,8 @@
 use std::{collections::HashMap, sync::Arc};
 
 use log::error;
-use smol::lock::Mutex;
 
-use crate::{util::random_16, Result};
+use crate::{async_runtime::lock::Mutex, util::random_16, Result};
 
 pub type ArcPublisher<T> = Arc<Publisher<T>>;
 pub type SubscriptionID = u16;
@@ -28,7 +27,7 @@ pub type SubscriptionID = u16;
 ///  
 /// ```
 pub struct Publisher<T> {
-    subs: Mutex<HashMap<SubscriptionID, smol::channel::Sender<T>>>,
+    subs: Mutex<HashMap<SubscriptionID, async_channel::Sender<T>>>,
 }
 
 impl<T: Clone> Publisher<T> {
@@ -43,7 +42,7 @@ impl<T: Clone> Publisher<T> {
     pub async fn subscribe(self: &Arc<Self>) -> Subscription<T> {
         let mut subs = self.subs.lock().await;
 
-        let chan = smol::channel::unbounded();
+        let chan = async_channel::unbounded();
 
         let mut sub_id = random_16();
 
@@ -84,7 +83,7 @@ impl<T: Clone> Publisher<T> {
 // Subscription
 pub struct Subscription<T> {
     id: SubscriptionID,
-    recv_chan: smol::channel::Receiver<T>,
+    recv_chan: async_channel::Receiver<T>,
     publisher: ArcPublisher<T>,
 }
 
@@ -93,7 +92,7 @@ impl<T: Clone> Subscription<T> {
     pub fn new(
         id: SubscriptionID,
         publisher: ArcPublisher<T>,
-        recv_chan: smol::channel::Receiver<T>,
+        recv_chan: async_channel::Receiver<T>,
     ) -> Subscription<T> {
         Self {
             id,
diff --git a/core/src/util/encode.rs b/core/src/util/encode.rs
index 7d1061b..bf63671 100644
--- a/core/src/util/encode.rs
+++ b/core/src/util/encode.rs
@@ -1,15 +1,14 @@
 use bincode::Encode;
 
-use crate::Result;
+use crate::{Error, Result};
 
 /// Encode the given type `T` into a `Vec<u8>`.
-pub fn encode<T: Encode>(msg: &T) -> Result<Vec<u8>> {
-    let vec = bincode::encode_to_vec(msg, bincode::config::standard())?;
+pub fn encode<T: Encode>(src: &T) -> Result<Vec<u8>> {
+    let vec = bincode::encode_to_vec(src, bincode::config::standard())?;
     Ok(vec)
 }
 
 /// Encode the given type `T` into the given slice..
-pub fn encode_into_slice<T: Encode>(msg: &T, dst: &mut [u8]) -> Result<()> {
-    bincode::encode_into_slice(msg, dst, bincode::config::standard())?;
-    Ok(())
+pub fn encode_into_slice<T: Encode>(src: &T, dst: &mut [u8]) -> Result<usize> {
+    bincode::encode_into_slice(src, dst, bincode::config::standard()).map_err(Error::from)
 }