Yielding for fairness

Cargo.toml

@@ -15,6 +15,7 @@ readme = "README.md"
 [dependencies]
 concurrent-queue = "1.2.2"
 event-listener = "2.4.0"
+fastrand = "1.3.4"
 futures-core = "0.3.5"
 
 [dev-dependencies]

src/lib.rs

@@ -235,6 +235,10 @@ impl<T> Sender<T> {
         let mut listener = None;
         let mut msg = msg;
 
+        if fastrand::usize(..100) == 0 {
+            yield_now().await;
+        }
+
         loop {
             // Attempt to send a message.
             match self.try_send(msg) {
@@ -490,6 +494,10 @@ impl<T> Receiver<T> {
     pub async fn recv(&self) -> Result<T, RecvError> {
         let mut listener = None;
 
+        if fastrand::usize(..100) == 0 {
+            yield_now().await;
+        }
+
         loop {
             // Attempt to receive a message.
             match self.try_recv() {
@@ -850,3 +858,23 @@ impl fmt::Display for TryRecvError {
         }
     }
 }
+
+async fn yield_now() {
+    pub struct YieldNow(bool);
+
+    impl Future for YieldNow {
+        type Output = ();
+
+        fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+            if !self.0 {
+                self.0 = true;
+                cx.waker().wake_by_ref();
+                Poll::Pending
+            } else {
+                Poll::Ready(())
+            }
+        }
+    }
+
+    YieldNow(false).await
+}