Release Lock Before Panicking (#12464)

async/event/feed.go

@@ -144,6 +144,7 @@ func (f *Feed) Send(value interface{}) (nsent int) {
 
 	if !f.typecheck(rvalue.Type()) {
 		f.sendLock <- struct{}{}
+		f.mu.Unlock()
 		panic(feedTypeError{op: "Send", got: rvalue.Type(), want: f.etype})
 	}
 	f.mu.Unlock()

async/event/feed_test.go

@@ -32,6 +32,8 @@ func TestFeedPanics(t *testing.T) {
 		f.Send(2)
 		want := feedTypeError{op: "Send", got: reflect.TypeOf(uint64(0)), want: reflect.TypeOf(0)}
 		assert.NoError(t, checkPanic(want, func() { f.Send(uint64(2)) }))
+		// Validate it doesn't deadlock.
+		assert.NoError(t, checkPanic(want, func() { f.Send(uint64(2)) }))
 	}
 	{
 		var f Feed