Create packages client/internal/ retry and lhttp.

client/internal/lhttp/utils.go

+// Copyright 2015 The Chromium 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 lhttp
+
+import (
+        "errors"
+        "net/url"
+        "strings"
+)
+
+// URLToHTTPS ensures the url is https://.
+func URLToHTTPS(s string) (string, error) {
+        u, err := url.Parse(s)
+        if err != nil {
+                return "", err
+        }
+        if u.Scheme != "" && u.Scheme != "https" {
+                return "", errors.New("Only https:// scheme is accepted. It can be omitted.")
+        }
+        if !strings.HasPrefix(s, "https://") {
+                s = "https://" + s
+        }
+        if _, err = url.Parse(s); err != nil {
+                return "", err
+        }
+        return s, nil
+}