stream/mts/meta/meta.go: using defer for m.mu.Unlock() Meta.Add()

stream/mts/meta/meta.go

@@ -79,15 +79,15 @@ func New() *Metadata {
 // Add adds metadata with key and val.
 func (m *Metadata) Add(key, val string) {
 	m.mu.Lock()
+	defer m.mu.Unlock()
 	m.data[key] = val
 	for _, k := range m.order {
 		if k == key {
-			m.mu.Unlock()
 			return
 		}
 	}
 	m.order = append(m.order, key)
-	m.mu.Unlock()
+	return
 }
 
 // All returns the a copy of the map containing the meta data.