event: improve fix for the goroutine leak in resubscribe

event/subscription.go

@@ -143,9 +143,8 @@ func (s *resubscribeSub) loop() {
 }
 
 func (s *resubscribeSub) subscribe() Subscription {
-	subscribed := make(chan error, 1)
+	subscribed := make(chan error)
 	var sub Subscription
-retry:
 	for {
 		s.lastTry = mclock.Now()
 		ctx, cancel := context.WithCancel(context.Background())
@@ -157,19 +156,19 @@ retry:
 		select {
 		case err := <-subscribed:
 			cancel()
-			if err != nil {
+			if err == nil {
-				// Subscribing failed, wait before launching the next try.
-				if s.backoffWait() {
-					return nil
-				}
-				continue retry
-			}
 				if sub == nil {
 					panic("event: ResubscribeFunc returned nil subscription and no error")
 				}
 				return sub
+			}
+			// Subscribing failed, wait before launching the next try.
+			if s.backoffWait() {
+				return nil // unsubscribed during wait
+			}
 		case <-s.unsub:
 			cancel()
+			<-subscribed // avoid leaking the s.fn goroutine.
 			return nil
 		}
 	}