http.go

// Copyright 2020 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.

package utils

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

// PostFile upload file
func PostFile(reader io.Reader, url, fieldname, filename string) (*http.Response, error) {
	bodyBuf := &bytes.Buffer{}
	bodyWriter := multipart.NewWriter(bodyBuf)

	// this step is very important
	fileWriter, err := bodyWriter.CreateFormFile(fieldname, filename)
	if err != nil {
		return nil, err
	}

	_, err = io.Copy(fileWriter, reader)
	if err != nil {
		return nil, err
	}

	contentType := bodyWriter.FormDataContentType()
	bodyWriter.Close()

	resp, err := http.Post(url, contentType, bodyBuf)
	if err != nil {
		return nil, err
	}

	return resp, nil
}