How to send a html templated body as an email through Gmail Go SDK?

Question

I have created a html file(i.e. email.html) which would finally serve me as my email body template. I tried the following code but my email body is a plain text with all the html that I have written in (email.html).

Can you suggest by looking into the code. Where is it going wrong??

Note: Template Parsing and Execute are working fine.

Code:

package main

import (
    "encoding/base64"
    "fmt"
    "html/template"
)

func getMessageString(fromEmail, To, ReplyTo, CC, BCC, Subject, emailBody string) []byte {
    return []byte("Reply-To: " + ReplyTo + "\r\n" + "From: " + fromEmail + "\r\n" + "To: " + To + "\r\n" + "Cc: " + CC + "\r\n" + "Bcc: " + BCC + "\r\n" + "Subject: " + Subject + "\r\n\r\n" + "MIME-Version: 1.0\r\n" + "Content-Type: text/html; charset=\"utf-8\"\r\n" + emailBody + "\r\n\r\n")
}

func main() {
    t, tempErr := template.New("template.html").ParseFiles("template.html")
    if tempErr != nil {
        fmt.Println(tempErr.Error())
        return
    }

    execErr := t.Execute(buf, data)
    if execErr != nil {
        fmt.Println(execErr.Error())
    } else {
        messageStr := getMessageString("[email protected]", "[email protected]", "[email protected]", "", "", "Test Subject", buf.String())

        var message gmail.Message
        message.Raw = base64.URLEncoding.EncodeToString(messageStr)

        _, err = svc.Users.Messages.Send("me", &message).Do()
        if err != nil {
            fmt.Println(err.Error())
        }
    }
}

Answer 1

The error is in the getMessageString func:

"Subject: " + Subject + "\r\n\r\n"

Notice the double \r\n sequence, mail server parses everything after double \r\n as email content. In your case it skipped Content-Type header. So just remove one \r\n and result code should look like:

func getMessageString(fromEmail, To, ReplyTo, CC, BCC, Subject, emailBody string) []byte {
    return []byte("Reply-To: " + ReplyTo + "\r\n" + "From: " + fromEmail + "\r\n" + "To: " + To + "\r\n" + "Cc: " + CC + "\r\n" + "Bcc: " + BCC + "\r\n" + "Subject: " + Subject + "\r\n" + "MIME-Version: 1.0\r\n" + "Content-Type: text/html; charset=\"utf-8\"\r\n\r\n" + emailBody + "\r\n")
}