创建要通过Google App Engine投放的tar文件

I'm writing an application for Google AppEngine using Go, and need to tar together a bunch of files to serve to the user when they navigate to a particular URL. At the moment the files are static, and so I could solve this problem by tarring them before upload to the server. In the future I would like to dynamically alter them before tarring, and so would like to learn how to tar & serve the static files on request.

In my init() function I have the following line:

http.HandleFunc("/download.tar", tarit)

The function tarit is the one I am having a problem with, and it currently looks like the following:

func tarit(w http.ResponseWriter, r *http.Request) {
    tarball := tar.NewWriter(w)
    defer tarball.Close()

    info, err := os.Stat("/files")
    if err != nil {
        return
    }

    var baseDir string
    if info.IsDir() {
        baseDir = filepath.Base("/files")
    }

    filepath.Walk("/files", func(path string, info os.FileInfo, err error) error {
        if err != nil {
            return err
        }
        header, err := tar.FileInfoHeader(info, info.Name())
        if err != nil {
            return err
        }

        if baseDir != "" {
            header.Name = filepath.Join(baseDir, strings.TrimPrefix(path, "/files"))
        }

        if err := tarball.WriteHeader(header); err != nil {
            return err
        }

        if info.IsDir() {
            return nil
        }

        file, err := os.Open(path)
        if err != nil {
            return err
        }
        defer file.Close()
        _, err = io.Copy(tarball, file)
        return err
    })
}

The files I am trying to add to the tarball are located in /files, and I've added this folder as a static_dir in the app.yaml.

When navigating to the appropriate URL, the browser downloads a tar file that is only 1 KB in size, and appears to be empty.

I would very much appreciate if someone could point out where I am going wrong, or what I am misunderstanding. I'd also be very happy to provide any other details that you would like.

Thanks!

Specify directories using paths relative to the directory containing app.yaml. The path in the posted code is the absolute path "/files". Perhaps you should change it to "files".

Log the errors returned from os.Stat and filepath.Walk. The errors will probably lead you to the problem.