Simple example of sending email with StartTLS in Go

starttls_example.go

/*
Simple example of sending an email with StartTLS in Go
See: https://golang.org/pkg/net/smtp/#SendMail for TLS defaults
*/

package main

import (
	"log"
	"net/smtp"
	"os"
)

const SMTP_USER_ENV string = "SMTP_USER"
const SMTP_PWD_ENV string = "SMTP_PWD"

const SMTP_ENDPOINT string = "email-smtp.us-east-1.amazonaws.com"
const SMTP_PORT string = ":587"

type Mail struct {
	ToName   string
	ToAddr   string
	FromName string
	FromAddr string
	Subject  string
	Body     string
}

func mailer(m Mail) error {

	smtp_user := os.Getenv(SMTP_USER_ENV)
	if smtp_user == "" {
		log.Fatal("Deploy: Unable to retrieve SMTP user. Make sure environment sets: " + SMTP_USER_ENV)
	}

	smtp_pwd := os.Getenv(SMTP_PWD_ENV)
	if smtp_pwd == "" {
		log.Fatal("Deploy: Unable to retrieve SMTP password. Make sure environment sets: " + SMTP_PWD_ENV)
	}

	mailer := SMTP_ENDPOINT

	msg := []byte(	"From: " +  m.FromName + " <" + m.FromAddr + ">" + "\r\n" +
			"To: " + m.ToAddr + "\r\n" +
			"Subject: " + m.Subject + "\r\n\r\n" +
			m.Body + "\r\n" )

	auth := smtp.PlainAuth("", smtp_user, smtp_pwd, mailer)
	err  := smtp.SendMail(mailer+SMTP_PORT, auth, m.FromAddr, []string{m.ToAddr}, msg)
	return err
}

func main() {

	m := Mail{	ToAddr: "recipient@example.com",
			FromName: "Sender's Name",
			FromAddr: "sender@example.com",
			Subject:  "Subject line",
			Body:     "Test email. \r\n Test, test." }

	err := mailer(m)
	if err != nil {
		log.Fatal(err)
	}
}