Added localhost to net.Listen() calls to avoid macOS firewall dialog. (#1539)

examples/helloworld/greeter_server/main.go

@@ -31,7 +31,7 @@ import (
 )
 
 const (
-	port = ":50051"
+	port = "50051"
 )
 
 // server is used to implement helloworld.GreeterServer.
@@ -43,7 +43,7 @@ func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloRe
 }
 
 func main() {
-	lis, err := net.Listen("tcp", port)
+	lis, err := net.Listen("tcp", "localhost:"+port)
 	if err != nil {
 		log.Fatalf("failed to listen: %v", err)
 	}