add vendoring with go dep

vendor/golang.org/x/net/http2/go19.go

@@ -0,0 +1,16 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.9
+
+package http2
+
+import (
+	"net/http"
+)
+
+func configureServer19(s *http.Server, conf *Server) error {
+	s.RegisterOnShutdown(conf.state.startGracefulShutdown)
+	return nil
+}