Error instead

src/delay.rs

@@ -5,6 +5,7 @@
 
 use std::fmt;
 use std::future::Future;
+use std::io;
 use std::pin::Pin;
 use std::sync::atomic::AtomicUsize;
 use std::sync::atomic::Ordering::SeqCst;
@@ -125,16 +126,19 @@ impl Delay {
 }
 
 impl Future for Delay {
-    type Output = ();
+    type Output = io::Result<()>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         let state = match self.state {
             Some(ref state) => state,
-            None => panic!("timer has gone away"),
+            None => {
+                let err = Err(io::Error::new(io::ErrorKind::Other, "timer has gone away"));
+                return Poll::Ready(err);
+            }
         };
 
         if state.state.load(SeqCst) & 1 != 0 {
-            return Poll::Ready(());
+            return Poll::Ready(Ok(()));
         }
 
         state.waker.register(&cx.waker());
@@ -143,8 +147,11 @@ impl Future for Delay {
         // state. If we've fired the first bit is set, and if we've been
         // invalidated the second bit is set.
         match state.state.load(SeqCst) {
-            n if n & 0b01 != 0 => Poll::Ready(()),
-            n if n & 0b10 != 0 => panic!("timer has gone away"),
+            n if n & 0b01 != 0 => Poll::Ready(Ok(())),
+            n if n & 0b10 != 0 => Poll::Ready(Err(io::Error::new(
+                io::ErrorKind::Other,
+                "timer has gone away",
+            ))),
             _ => Poll::Pending,
         }
     }