Upload to a multipart/form-data form

upload.go

func UploadPosts(file, date, name, comment, url string) (err error) {
	// Make a new multipart writer with a buffer
	var b bytes.Buffer
	w := multipart.NewWriter(&b)

        // This is just a random form field
	if err = w.WriteField("name", name); err != nil {
		return
	}

	if err = w.WriteField("comment", comment); err != nil {
		return
	}

	if err = w.WriteField("date", date); err != nil {
		return
	}

        // This just takes a string of the file name
	if file != "" {

		filename := img_dir + file

		f, err := os.Open(filename)
		if err != nil {
			return err
		}

                // CreateFormFile adds the file to the multipart writer
		fw, err := w.CreateFormFile("file", filename)
		if err != nil {
			return err
		}
		
		if _, err = io.Copy(fw, f); err != nil {
			return err
		}

	}

        // Close the multipart writer
	w.Close()

	// Make a post request with our writer
	req, err := http.NewRequest("POST", url, &b)
	if err != nil {
		return
	}
	// Adds content-type header
	req.Header.Add("Content-Type", w.FormDataContentType())

	// create http client and execute request with Do()
	client := &http.Client{}
	res, err := client.Do(req)
	if err != nil {
		return
	}
	defer res.Body.Close()
	
        // DumpResponse just to check for error messages
	body, err := httputil.DumpResponse(res, true)
	if err != nil {
		return
	}

        // Print anything to stdout
	fmt.Println(string(body))

	return
}