multipart-reader.go

if r.Method != "POST" {
	http.Error(w, "Only accept POST request", http.StatusBadRequest)
	return
}

basePath, _ := os.Getwd()

reader, err := r.MultipartReader()
if err != nil {
	http.Error(w, err.Error(), http.StatusInternalServerError)
	return
}

for {
	part, err := reader.NextPart()
	if err == io.EOF {
		break
	}

	fileLocation := filepath.Join(basePath, "files", part.FileName()) // target folder
	dst, err := os.Create(fileLocation)
	if dst != nil {
		defer dst.Close()
	}
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	if _, err := io.Copy(dst, part); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
}

w.Write([]byte(`all files uploaded`))