Fix issue #167 - Concurrent write/write of in-flight shard map (#168)

consumer.go

@@ -313,32 +313,22 @@ func isShardClosed(nextShardIterator, currentShardIterator *string) bool {
 }
 
 type shards struct {
-	*sync.RWMutex
-	shardsInProcess map[string]struct{}
+	shardsInProcess sync.Map
 }
 
 func newShardsInProcess() *shards {
-	return &shards{
-		RWMutex:         &sync.RWMutex{},
-		shardsInProcess: make(map[string]struct{}),
-	}
+	return &shards{}
 }
 
 func (s *shards) addShard(shardId string) {
-	s.Lock()
-	defer s.Unlock()
-	s.shardsInProcess[shardId] = struct{}{}
+	s.shardsInProcess.Store(shardId, struct{}{})
 }
 
 func (s *shards) doesShardExist(shardId string) bool {
-	s.RLock()
-	defer s.RUnlock()
-	_, ok := s.shardsInProcess[shardId]
+	_, ok := s.shardsInProcess.Load(shardId)
 	return ok
 }
 
 func (s *shards) deleteShard(shardId string) {
-	s.Lock()
-	defer s.Unlock()
-	delete(s.shardsInProcess, shardId)
+	s.shardsInProcess.Delete(shardId)
 }