Don't close closed channels

http/service.go

@@ -270,10 +270,8 @@ type Service struct {
 // the service performs no authentication and authorization checks.
 func New(addr string, store Store, cluster Cluster, credentials CredentialStore) *Service {
 	return &Service{
-		closeCh:             make(chan struct{}),
 		addr:                addr,
 		store:               store,
-		queueDone:           make(chan struct{}),
 		DefaultQueueCap:     1024,
 		DefaultQueueBatchSz: 128,
 		DefaultQueueTimeout: 100 * time.Millisecond,
@@ -311,6 +309,9 @@ func (s *Service) Start() error {
 	}
 	s.ln = ln
 
+	s.closeCh = make(chan struct{})
+	s.queueDone = make(chan struct{})
+
 	s.stmtQueue = queue.New(s.DefaultQueueCap, s.DefaultQueueBatchSz, s.DefaultQueueTimeout)
 	go s.runQueue()
 	s.logger.Printf("execute queue processing started with capacity %d, batch size %d, timeout %s",
@@ -330,7 +331,11 @@ func (s *Service) Start() error {
 // Close closes the service.
 func (s *Service) Close() {
 	s.stmtQueue.Close()
-	close(s.closeCh)
+	select {
+	case <-s.closeCh:
+	default:
+		close(s.closeCh)
+	}
 	s.ln.Close()
 	return
 }

queue/queue.go

@@ -56,8 +56,12 @@ func (q *Queue) Flush() error {
 
 // Close closes the queue. A closed queue should not be used.
 func (q *Queue) Close() error {
-	close(q.done)
-	<-q.closed
+	select {
+	case <-q.done:
+	default:
+		close(q.done)
+		<-q.closed
+	}
 	return nil
 }