How can I send a POST request with Content-Type: multipart/form-data in Go, while including both []byte parameters and string arguments, given that my previous attempts have resulted in a 301 Moved Pe

Can I post with Content-Type: multipart/form-data?

Question:

How can I send a POST request with Content-Type: multipart/form-data while including both []byte parameters and string arguments? Previous attempts have resulted in the following error:

[301 301 Moved Permanently]<...HTML response body...>

Provided Go Code:

<code class="go">func NewPost2(url string) ([]byte, error) {
    m := make(map[string]interface{}, 0)
    m["fileName"] ="good"
    m["name"] = Base64ToByte("/9j/4AAQSkZJRgABAQEAeAB4AAD/2wBDAAIBAQIBAQICAgICAgICAwUDAwMDAwYEBAMFBwYHBwcGBwcICQsJCAgKCAcHCg0KCgsMDAwMBwkODw0MDgsMDAz/2wBDAQICAgMDAwYDAwYMCAcIDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAz/wAARCAABAAEDASIAAhEBAxEB/8QAHwAAAQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQRBRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RFRkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ipqrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/8QAHwEAAwEBAQEBAQEBAQAAAAAAAAECAwQFBgcICQoL/8QAtREAAgECBAQDBAcFBAQAAQJ3AAECAxEEBSExBhJBUQdhcRMiMoEIFEKRobHBCSMzUvAVYnLRChYkNOEl8RcYGRomJygpKjU2Nzg5OkNERUZHSElKU1RVVldYWVpjZGVmZ2hpanN0dXZ3eHl6goOEhYaHiImKkpOUlZaXmJmaoqOkpaanqKmqsrO0tba3uLm6wsPExcbHyMnK0tPU1dbX2Nna4uPk5ebn6Onq8vP09fb3+Pn6/9oADAMBAAIRAxEAPwDHooor+wD+Zz//2Q==")
    b, _ := json.Marshal(m)

    httpReq, err := http.NewRequest("POST", url, bytes.NewBuffer(b))
    httpReq.Header.Set("Content-Type", "multipart/form-data;charset=UTF-8")

    client := &amp;http.Client{}
    resp, err := client.Do(httpReq)
    if err != nil {
        return nil, err
    }

    defer resp.Body.Close()

    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))
    }

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

    return respData, nil
}</code>

Answer:

The provided code attempted to send []byte parameters as JSON in the request body, which is not an appropriate format for multipart/form-data submissions.

To correct this issue, we can use multipart/form-data encoding with the following updated code:

<code class="go">func NewPostFile(url string, paramTexts map[string]interface{}, paramFile FileItem) ([]byte, error) {
// if paramFiles ==nil {
//  return NewPost(url,paramTexts,header,transport)
// }

// Create a new multipart writer
bodyBuf := &amp;bytes.Buffer{}
bodyWriter := multipart.NewWriter(bodyBuf)

// Write text parameters to the multipart writer
for k, v := range paramTexts {
    bodyWriter.WriteField(k, v.(string))
}

// Write the file content to the multipart writer
fileWriter, err := bodyWriter.CreateFormFile(paramFile.Key, paramFile.FileName)
if err != nil {
    fmt.Println(err)
    //fmt.Println("Create form file error: ", error)
    return nil, err
}
fileWriter.Write(paramFile.Content)

// Close the multipart writer
bodyWriter.Close()

// Set the Content-Type header to multipart/form-data
contentType := bodyWriter.FormDataContentType()

// Create the POST request with the multipart/form-data body
resp, err := http.Post(url, contentType, bodyBuf)
if err != nil {
    return nil, err
}

// Handle and process the HTTP response
// ... (remainder of code omitted for brevity)</code>

By using multipart/form-data encoding and correctly handling the file parameters, we can now successfully POST with []byte parameters and string arguments.

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