fix: topic data race

Signed-off-by: gfanton <8671905+gfanton@users.noreply.github.com>

sync_inmem_provider.go

@@ -80,7 +80,7 @@ func (ps *PubSub) getOrCreateTopic(ns string) *PubSubSubscribers {
 }
 
 func (ps *PubSub) Register(pid peer.ID, ns string, addrs [][]byte, ttlAsSeconds int, counter uint64) {
-	subscribers := ps.getOrCreateTopic(ns)
+	topic := ps.getOrCreateTopic(ns)
 	dataToSend := &pb.RegistrationRecord{
 		Id:    pid.String(),
 		Addrs: addrs,
@@ -88,16 +88,15 @@ func (ps *PubSub) Register(pid peer.ID, ns string, addrs [][]byte, ttlAsSeconds
 		Ttl:   time.Now().Add(time.Duration(ttlAsSeconds) * time.Second).UnixMilli(),
 	}
 
-	subscribers.mu.Lock()
-	subscribers.lastAnnouncement = dataToSend
-	toNotify := subscribers.subscribers
-	subscribers.mu.Unlock()
-
+	topic.mu.Lock()
+	topic.lastAnnouncement = dataToSend
+	toNotify := topic.subscribers
 	for _, stream := range toNotify {
 		if err := stream.WriteMsg(dataToSend); err != nil {
 			log.Errorf("unable to notify rendezvous data update: %s", err.Error())
 		}
 	}
+	topic.mu.Unlock()
 }
 
 func (ps *PubSub) Unregister(p peer.ID, ns string) {
@@ -144,13 +143,12 @@ func (ps *PubSub) handleStream(s inet.Stream) {
 		topic.subscribers[s.Conn().RemotePeer()] = w
 		subscribedTopics[req.DiscoverSubscribe.Ns] = struct{}{}
 		lastAnnouncement := topic.lastAnnouncement
-		topic.mu.Unlock()
-
 		if lastAnnouncement != nil {
 			if err := w.WriteMsg(lastAnnouncement); err != nil {
 				log.Errorf("unable to write announcement: %s", err.Error())
 			}
 		}
+		topic.mu.Unlock()
 	}
 }