使用golang中的gmail API发送带有附件的电子邮件

Question

I have followed https://developers.google.com/gmail/api/quickstart/go. I modified the scope to gmail.MailGoogleComScope and tried sending email. The email gets sent. However, the attachment is not getting sent. It does not give any error as well. Please note the call to Media function is what I tried looking at the code in gmail API, not sure if that is the right way.

When I set the contentType to application/png, the API throws an exception with the message 'png not supported, use message/rfc822'. Following is the code for SendEmail.

func SendEmail(msg EmailMessage) {
  ctx := context.Background()

  b, err := ioutil.ReadFile("/tmp/client_secret.json")
  if err != nil {
    log.Fatalf("Unable to read client secret file: %v", err)
  }

  config, err := google.ConfigFromJSON(b, gmail.MailGoogleComScope)
  if err != nil {
    log.Fatalf("Unable to parse client secret file to config: %v", err)
  }
  client := getClient(ctx, config)

  srv, err := gmail.New(client)
  if err != nil {
    log.Fatalf("Unable to retrieve gmail Client %v", err)
  }

  var message gmail.Message
  temp := []byte("From: 'me'
" +
    "reply-to: [e-mail]
" +
    "To:  " + msg.To + "
" +
    "Subject: " + msg.Subject + "
" +
    "
" + msg.Body)

  message.Raw = base64.StdEncoding.EncodeToString(temp)
  message.Raw = strings.Replace(message.Raw, "/", "_", -1)
  message.Raw = strings.Replace(message.Raw, "+", "-", -1)
  message.Raw = strings.Replace(message.Raw, "=", "", -1)

  imgFile, err := os.Open("image.png") // a QR code image

  if err != nil {
    log.Fatalf("Error in opening file")
  }
  defer imgFile.Close()

  mediaOptions := googleapi.ContentType("message/rfc822")
  _, err = srv.Users.Messages.Send("me", &message).Media(imgFile,  mediaOptions).Do()
  if err != nil {
    log.Fatalf("Unable to send. %v", err)
  }
}

Please suggest what is missing

Answer 1

I were having the same issue, after long time reading find a library that support attachments https://github.com/jordan-wright/email