Migrate to Go modules

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

gateway/vendor/google.golang.org/protobuf/internal/impl/enum.go

@@ -0,0 +1,21 @@
+// Copyright 2019 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 impl
+
+import (
+	"reflect"
+
+	pref "google.golang.org/protobuf/reflect/protoreflect"
+)
+
+type EnumInfo struct {
+	GoReflectType reflect.Type // int32 kind
+	Desc          pref.EnumDescriptor
+}
+
+func (t *EnumInfo) New(n pref.EnumNumber) pref.Enum {
+	return reflect.ValueOf(n).Convert(t.GoReflectType).Interface().(pref.Enum)
+}
+func (t *EnumInfo) Descriptor() pref.EnumDescriptor { return t.Desc }