Avoid beeing stuck in hub lock when a client gets replaced but the old connection does not hang on close.

src/app/spreed-webrtc-server/hub.go

@@ -154,8 +154,12 @@ func (h *hub) OnConnect(client Client, session *Session) {
 	log.Printf("Created client %d with id %s\n", client.Index(), session.Id)
 	// Register connection or replace existing one.
 	if ec, ok := h.clients[session.Id]; ok {
-		log.Printf("Closing obsolete client %d with id %s\n", ec.Index(), session.Id)
-		ec.ReplaceAndClose()
+		// Clean up old client at the end and make sure to run this in another go routine,
+		// to avoid blocking the new client if the old one hangs or whatever.
+		defer func() {
+			log.Printf("Closing obsolete client %d with id %s\n", ec.Index(), session.Id)
+			go ec.ReplaceAndClose()
+		}()
 	}
 	h.clients[session.Id] = client
 	h.mutex.Unlock()