Merge pull request #540 from iamqizhao/master

refine the comments of grpc.Server.Stop()
diff --git a/server.go b/server.go
index d71c094..19a002a 100644
--- a/server.go
+++ b/server.go
@@ -594,8 +594,9 @@
-// Stop stops the gRPC server. Once Stop returns, the server stops accepting
-// connection requests and closes all the connected connections.
+// Stop stops the gRPC server. It immediately closes all open connections and listeners. It cancels all
+// active RPCs on server side and the corresponding pending RPCs on client side will get notified by
+// connection errors.
 func (s *Server) Stop() {
 	listeners := s.lis