fix negotiation blocked when channel closed

client.go

@@ -624,7 +624,12 @@ func (c *Client) Negotiate(offer webrtc.SessionDescription) (*webrtc.SessionDesc
 		ErrorChan:  errorChan,
 	})
 
+	localCtx, cancel := context.WithCancel(c.context)
+	defer cancel()
+
 	select {
+	case <-localCtx.Done():
+		return nil, ErrClientStoped
 	case err := <-errorChan:
 		return nil, err
 	case answer := <-answerChan:

queue.go

@@ -57,6 +57,10 @@ func (q *queue) Push(item interface{}) {
 
 		if !q.IsOpen.Load() {
 			glog.Warning("sfu: queue is closed when push renegotiation")
+			if opItem, ok := item.(negotiationQueue); ok {
+				opItem.ErrorChan <- ErrQueueIsClosed
+			}
+
 			return
 		}