在可恢复上传谷歌云存储中丢失文件属性

Question

func StoreUpload(c appengine.Context, cn context.Context, contentType string, filename string, email string, origin string) (string, string, error) {
    uuid, err := UUID()

    if err != nil{
        return "", "", err
    }

    filename = uuid + filename[len(filename)-4:]

    tokenSource := google.AppEngineTokenSource(cn, storage.ScopeFullControl)

    token, err := tokenSource.Token()

    if err != nil{
        return "", "", err
    }

    metaBody := []byte("{ \"metadata\": { \"x-goog-meta-uploader\": \""+ email +"\" }}")

    req, err := http.NewRequest(
        "POST",
        fmt.Sprintf("https://www.googleapis.com/upload/storage/v1/b/%s/o?uploadType=resumable&name=upload/%s", models.HYLIGHT_EXTERNAL_BUCKET, filename),
        bytes.NewReader(metaBody),
    )

    req.Header.Set("Authorization", "Bearer " + token.AccessToken)
    req.Header.Set("X-Upload-Content-Type", contentType)
    req.Header.Set("Content-Type", "application/json; charset=UTF-8")
    req.Header.Set("Content-Length", fmt.Sprint(len(metaBody)))
    req.Header.Set("Origin", origin)

    client := &http.Client{
        Transport:  &urlfetch.Transport{
            Context: c,
            Deadline: 20 * time.Second,
        },
    }

    res, err := client.Do(req)

    if err != nil{
        return "", "", err
    }

    return res.Header.Get("Location"), filename, err
}

google cloud bucket中的结果将具有正确的video/mp4 mimetype（这是由浏览器决定的），但仍然无法在浏览器上查看。

编辑：

我也尝试过使用chrome扩展名“Postman”在收到一个可恢复的上传链接后上传一个文件，但它的属性在上传到GCS时也会丢失，所以它似乎与将文件上传到GCS时涉及的JS端无关。