broker memory: fix issue with publish/subscribe

mutex locking have errors, so when two service (one pub, other sub)
try to use this broker it waits for mutex release and nothing works

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

broker/memory/memory.go

@@ -72,14 +72,14 @@ func (m *memoryBroker) Init(opts ...broker.Option) error {
 }
 
 func (m *memoryBroker) Publish(topic string, message *broker.Message, opts ...broker.PublishOption) error {
-	m.Lock()
-	defer m.Unlock()
-
+	m.RLock()
 	if !m.connected {
+		m.RUnlock()
 		return errors.New("not connected")
 	}
 
 	subs, ok := m.Subscribers[topic]
+	m.RUnlock()
 	if !ok {
 		return nil
 	}
@@ -99,12 +99,12 @@ func (m *memoryBroker) Publish(topic string, message *broker.Message, opts ...br
 }
 
 func (m *memoryBroker) Subscribe(topic string, handler broker.Handler, opts ...broker.SubscribeOption) (broker.Subscriber, error) {
-	m.Lock()
-	defer m.Unlock()
-
+	m.RLock()
 	if !m.connected {
+		m.RUnlock()
 		return nil, errors.New("not connected")
 	}
+	m.RUnlock()
 
 	var options broker.SubscribeOptions
 	for _, o := range opts {
@@ -119,7 +119,9 @@ func (m *memoryBroker) Subscribe(topic string, handler broker.Handler, opts ...b
 		opts:    options,
 	}
 
+	m.Lock()
 	m.Subscribers[topic] = append(m.Subscribers[topic], sub)
+	m.Unlock()
 
 	go func() {
 		<-sub.exit