Send multipart form data in go

multipart-form-data.go

package main

import (
  "bytes"
	"mime/multipart"
	"net/http"
)

func PostFormMultipart(content []byte) (*http.Response, error) {
	url := "http://localhost:8080"

	body := &bytes.Buffer{}
	writer := multipart.NewWriter(body)
	part, err := writer.CreateFormFile("fieldname", "filename.txt")
	if err != nil {
		return nil, err
	}
	part.Write(content)
	err = writer.Close()
	if err != nil {
		return nil, err
	}
	req, err := http.NewRequest("POST", url, body)
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", writer.FormDataContentType())
	return http.DefaultClient.Do(req)
}