Use Go1.11 module (#5743)

* Migrate to go modules

* make vendor

* Update mvdan.cc/xurls

* make vendor

* Update code.gitea.io/git

* make fmt-check

* Update github.com/go-sql-driver/mysql

* make vendor

vendor/google.golang.org/appengine/internal/metadata.go

@@ -0,0 +1,60 @@
+// Copyright 2014 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+package internal
+
+// This file has code for accessing metadata.
+//
+// References:
+//	https://cloud.google.com/compute/docs/metadata
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+)
+
+const (
+	metadataHost = "metadata"
+	metadataPath = "/computeMetadata/v1/"
+)
+
+var (
+	metadataRequestHeaders = http.Header{
+		"Metadata-Flavor": []string{"Google"},
+	}
+)
+
+// TODO(dsymonds): Do we need to support default values, like Python?
+func mustGetMetadata(key string) []byte {
+	b, err := getMetadata(key)
+	if err != nil {
+		panic(fmt.Sprintf("Metadata fetch failed for '%s': %v", key, err))
+	}
+	return b
+}
+
+func getMetadata(key string) ([]byte, error) {
+	// TODO(dsymonds): May need to use url.Parse to support keys with query args.
+	req := &http.Request{
+		Method: "GET",
+		URL: &url.URL{
+			Scheme: "http",
+			Host:   metadataHost,
+			Path:   metadataPath + key,
+		},
+		Header: metadataRequestHeaders,
+		Host:   metadataHost,
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("metadata server returned HTTP %d", resp.StatusCode)
+	}
+	return ioutil.ReadAll(resp.Body)
+}