title: Go: http file upload
body: <p>I am trying to upload a file as an attachment from a client written in Go.
  I am using http multipart CreateFormFile. When I do this, it sends the data in body to the server which server rejects.</p>
  
  <pre><code>file, err := os.Open(*img.Filepath)
  if err != nil {
      return err
  }
  
  defer file.Close()
  
  body := &amp;bytes.Buffer{}
  writer := multipart.NewWriter(body)
  part, err := writer.CreateFormFile("asset", filepath.Base(*img.Filepath))
  if err != nil {
      return err
  }
  _, err = io.Copy(part, file)
  if err != nil {
      return err
  }
  
  contentType := writer.FormDataContentType()
  err = writer.Close()
  if err != nil {
      return err
  }
  
  request, err := http.NewRequest("POST", API_URL, body)
  if err != nil {
      return err
  }
  
  request.Header.Set("Content-Type", contentType)
  
  values := request.URL.Query()
  values.Add("filename", util.GetFileNameWithoutExtension(*img.FileName))
  request.URL.RawQuery = values.Encode()
  client := &amp;http.Client{}
  resp, err := client.Do(request)
  if err != nil {
      return err
  } else {
      respBody := &amp;bytes.Buffer{}
      _, err = respBody.ReadFrom(resp.Body)
      if err != nil {
          return err
      }
      resp.Body.Close()
  }
  </code></pre>
  
  <p>When I try the same using curl it works
  curl -X POST -F "<strong>asset=@filepath</strong>" "<a href="http://localhost/api/v1/xyz?filename=filename" rel="nofollow">http://localhost/api/v1/xyz?filename=filename</a>"</p>
  
  <p>How can I implement key=@val functionality with Go?</p>