Attaching image to email sent through golang gmail api

Question

I'm trying to attach a picture to an email sent through the gmail golang api, but the image does not attach. I've looked extensively at the documentation, but I have not been able to figure out how to attach an image to an email. Here is the code that I have so far. It only sends the text.

// SendEmailEmbed2 Sends email through gmail
func (config *GmailConfig) SendEmailEmbed2(person int, formattedTemplate string) {

    msg := formattedTemplate

    mmbody := gmail.MessagePartBody{
        Data: encodeWeb64String([]byte(msg)),
    }

    headers := []*gmail.MessagePartHeader{
        &gmail.MessagePartHeader{
            Name:  "From",
            Value: config.FromAddress,
        },
        &gmail.MessagePartHeader{
            Name:  "To",
            Value: config.CSVReference.Elem(person, config.PlugIns[0].ToEmail).String(),
        },
        &gmail.MessagePartHeader{
            Name:  "Subject",
            Value: config.EmailSubject,
        },
        &gmail.MessagePartHeader{
            Name:  "Content-Disposition",
            Value: "./prac2_files/image001.jpg",
        },
    }

    Parts := []*gmail.MessagePart{
        &gmail.MessagePart{
            Filename: "./prac2_files/image001.jpg",
        },
    }

    partgmsg := gmail.MessagePart{
        Body: &mmbody,

        Headers: headers,

        Parts: Parts,

        MimeType: "multipart",
    }

    im, _ := os.Open("./prac2_files/image001.jpg")
    gmsg := gmail.Message{
        Payload: &partgmsg,
        Raw:     encodeWeb64String([]byte(msg)),
    }
    call, err := config.srv.Users.Messages.Send("me", &gmsg).Media(im).Do()

    im.Close()
    if err != nil {
        log.Println("em %v, err %v", gmsg, err)
        // return err
    }
    // return err 

    fmt.Println(person, ":", headers[1].Value, " : ", call.LabelIds)
}

func encodeWeb64String(b []byte) string {

    s := base64.URLEncoding.EncodeToString(b)

    var i = len(s) - 1
    for s[i] == '=' {
        i--
    }

    return s[0 : i+1]
}

Answer 1

Answer:

You need to attach the file inline in the body of the message.

Code:

message := gmail.Message

attachmentBytes := ioutil.ReadFile(fileDir + fileName)

attachmentMimeType: = http.DetectContentType(attachmentBytes)

attachmentData: = base64.StdEncoding.EncodeToString(attachmentBytes)

boundary: = randStr(32, "alphanum")

messageBody: = [] byte("Content-Type: multipart/mixed; boundary=" + boundary + " \n" +
    "MIME-Version: 1.0\n" +
    "to: " + config.CSVReference.Elem(person, config.PlugIns[0].ToEmail).String() + "\n" +
    "from: " + config.FromAddress + "\n" +
    "subject: " + config.EmailSubject + "\n\n" +

    "--" + boundary + "\n" +
    "Content-Type: text/plain; charset=" + string('"') + "UTF-8" + string('"') + "\n" +
    "MIME-Version: 1.0\n" +
    "Content-Transfer-Encoding: 7bit\n\n" +
    content + "\n\n" +
    "--" + boundary + "\n" +

    "Content-Type: " + "image/jpg" + "; name=" + string('"') + fileName + string('"') + " \n" +
    "MIME-Version: 1.0\n" +
    "Content-Transfer-Encoding: base64\n" +
    "Content-Disposition: attachment; filename=" + string('"') + fileName + string('"') + " \n\n" +
    chunkSplit(attachmentData, 76, "\n") +
    "--" + boundary + "--")

message.Raw = base64.URLEncoding.EncodeToString(messageBody)

_, err := service.Users.Messages.Send("me", &message).Do()
if err != nil {
    log.Fatalf("Email sending failed: %v", err)
} else {
    log.Println("Email message sent")
}