Go で「Content-Type: multipart/form-data」を使用して投稿するときの「[301 301 Moved Permanently]」エラーを解決する方法

<code class="go">func NewPostFile(url string, paramTexts map[string]interface{}, paramFile FileItem) ([]byte, error) {
    // Create a multipart body buffer and writer
    bodyBuf := &bytes.Buffer{}
    bodyWriter := multipart.NewWriter(bodyBuf)

    // Add string parameters
    for k, v := range paramTexts {
        bodyWriter.WriteField(k, v.(string))
    }

    // Add file parameter
    fileWriter, err := bodyWriter.CreateFormFile(paramFile.Key, paramFile.FileName)
    if err != nil {
        return nil, err
    }
    fileWriter.Write(paramFile.Content)

    // Set content type
    contentType := bodyWriter.FormDataContentType()

    // Close the writer
    bodyWriter.Close()

    resp, err := http.Post(url, contentType, bodyBuf)
    if err != nil {
        return nil, err
    }
    defer resp.Body.Close()

    // Handle response status
    if resp.StatusCode < 200 || resp.StatusCode >= 300 {
        b, _ := ioutil.ReadAll(resp.Body)
        return nil, fmt.Errorf("[%d %s]%s", resp.StatusCode, resp.Status, string(b))
    }

    // Read response data
    respData, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        return nil, err
    }

    return respData, nil
}

// Define FileItem type to represent file parameters
type FileItem struct {
    Key       string // e.g. "image_content"
    FileName  string // e.g. "test.jpg"
    Content   []byte // Byte array of the file
}</code>