Golang http multipart post upload/sent progress tracker.

http-post-progress.go

package main

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"mime/multipart"
	"net/http"
	"os"
)

type Tracker struct {
	io.Reader
	sent int
}

func (r *Tracker) Read(p []byte) (n int, err error) {
	n, err = r.Reader.Read(p)
	r.sent += n
	fmt.Printf("Read %d bytes\r", r.sent)
	return
}

// Close the reader when it implements io.Closer
func (r *Tracker) Close() (err error) {
	if closer, ok := r.Reader.(io.Closer); ok {
		return closer.Close()
	}
	return
}

func main() {
	body := &bytes.Buffer{}
	bodyWriter := multipart.NewWriter(body)

	fw, _ := bodyWriter.CreateFormFile("file", "file")
	fh, _ := os.Open("file")

	io.Copy(fw, fh)
	bodyWriter.Close()

	reader := &Tracker{body, 0}

	resp, _ := http.Post("http://httpbin.org/post", bodyWriter.FormDataContentType(), reader)
	defer resp.Body.Close()

	response, _ := ioutil.ReadAll(resp.Body)
	print(string(response))
}