use write-only mutex

kv/memberlist/memberlist_client.go

@@ -253,7 +253,7 @@ type KV struct {
 	messageCounter       int // Used to give each message in the sentMessages and receivedMessages a unique ID, for UI.
 
 	// Per-key value update workers
-	workersMu       sync.RWMutex
+	workersMu       sync.Mutex
 	workersChannels map[string]chan valueUpdate
 
 	// closed on shutdown