Merge pull request #762 from LK4D4/prevent_double_close

server: close only non-closed listeners

server.go

@@ -320,9 +320,11 @@ func (s *Server) Serve(lis net.Listener) error {
 	s.lis[lis] = true
 	s.mu.Unlock()
 	defer func() {
-		lis.Close()
 		s.mu.Lock()
+		if s.lis != nil && s.lis[lis] {
+			lis.Close()
 			delete(s.lis, lis)
+		}
 		s.mu.Unlock()
 	}()
 	for {