Migrate to Go modules

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

gateway/vendor/google.golang.org/protobuf/proto/proto.go

@@ -0,0 +1,34 @@
+// Copyright 2018 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.
+
+package proto
+
+import (
+	"google.golang.org/protobuf/internal/errors"
+	"google.golang.org/protobuf/reflect/protoreflect"
+)
+
+// Message is the top-level interface that all messages must implement.
+// It provides access to a reflective view of a message.
+// Any implementation of this interface may be used with all functions in the
+// protobuf module that accept a Message, except where otherwise specified.
+//
+// This is the v2 interface definition for protobuf messages.
+// The v1 interface definition is "github.com/golang/protobuf/proto".Message.
+//
+// To convert a v1 message to a v2 message,
+// use "github.com/golang/protobuf/proto".MessageV2.
+// To convert a v2 message to a v1 message,
+// use "github.com/golang/protobuf/proto".MessageV1.
+type Message = protoreflect.ProtoMessage
+
+// Error matches all errors produced by packages in the protobuf module.
+//
+// That is, errors.Is(err, Error) reports whether an error is produced
+// by this module.
+var Error error
+
+func init() {
+	Error = errors.Error
+}