You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: urls.go
    path of file: ./repos/juju/environs/utils
    
    the code of the file until where you have to start completion: // Copyright 2014 Canonical Ltd.
// Copyright 2014 Cloudbase Solutions SRL
// Licensed under the AGPLv3, see LICENCE file for details.

package utils

import (
	"fmt"
	"net/url"
	"
    
func GetURL(source, basePath string) (string, error) {
	// If source is a raw directory, we need to append the file:// prefix
	// so it can be used as a URL.
	defaultURL := source
	u, err := url.Parse(source)
	if err != nil {
		return "", fmt.Errorf("invalid default %s URL %s: %v", basePath, defaultURL, err)
	}

	switch u.Scheme {
	case "http", "https", "file", "test":
		return source, nil
	}

	if filepath.IsAbs(defaultURL) {
		defaultURL = utils.MakeFileURL(defaultURL)
		if !strings.HasSuffix(defaultURL, "/"+basePath) {
			defaultURL = fmt.Sprintf("%s/%s", defaultURL, basePath)
		}
	} else {
		return "", fmt.Errorf("%s is not an absolute path", source)
	}
	return defaultURL, nil
}