server_test: add Serve()/Shutdown() race test.

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

server_test.go

@@ -298,6 +298,36 @@ func TestServerClose(t *testing.T) {
 	checkServerShutdown(t, server)
 }
 
+func TestImmediateServerShutdown(t *testing.T) {
+	var (
+		ctx            = context.Background()
+		server         = mustServer(t)(NewServer())
+		addr, listener = newTestListener(t)
+		errs           = make(chan error, 1)
+		_, cleanup     = newTestClient(t, addr)
+	)
+	defer cleanup()
+	defer listener.Close()
+	go func() {
+		time.Sleep(1 * time.Millisecond)
+		errs <- server.Serve(ctx, listener)
+	}()
+
+	registerTestingService(server, &testingServer{})
+
+	if err := server.Shutdown(ctx); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case err := <-errs:
+		if err != ErrServerClosed {
+			t.Fatal(err)
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("retreiving error from server.Shutdown() timed out")
+	}
+}
+
 func TestOversizeCall(t *testing.T) {
 	var (
 		ctx             = context.Background()