go / smtp で添付ファイル付きメール送信

sendmail_with_attachment.go

package main

import (
	"crypto/tls"
	"fmt"
	"net/mail"
	"net/smtp"

	"github.com/scorredoira/email"
)

const (
	MAIL_SUBJECT = "mail subject"
	MAIL_BODY    = "body"
	FROM_NAME    = "from_name"
	FROM_ADDRESS = "from@example.com"
	TO_ADDRESS   = "to@example.com"
	CSV_FILENAME = "test.csv"
)

func buildCSV() string {
	return "asdf,fuga,piyo"
}

func sendMail() error {
	m := email.NewMessage(MAIL_SUBJECT, MAIL_BODY)
	m.From = mail.Address{Name: FROM_NAME, Address: FROM_ADDRESS}
	m.To = []string{TO_ADDRESS}

	if err := m.AttachBuffer(CSV_FILENAME, []byte(buildCSV()), false); err != nil {
		return err
	}

	auth := smtp.PlainAuth("", "example@gmail.com", "password", "smtp.gmail.com")
	tlsconfig := &tls.Config{
		InsecureSkipVerify: true,
		ServerName:         "smtp.gmail.com",
	}
	conn, err := tls.Dial("tcp", "smtp.gmail.com:465", tlsconfig)
	if err != nil {
		fmt.Println("tls dial error")
		return err
	}
	c, err := smtp.NewClient(conn, "smtp.gmail.com")
	if err != nil {
		fmt.Println("smtp client error")
		return err
	}
	if err := c.Auth(auth); err != nil {
		fmt.Println("smtp auth error")
		return err
	}

	// To && From
	if err = c.Mail("from@example.com"); err != nil {
		fmt.Println("smtp from error")
		return err
	}

	if err = c.Rcpt("to@example.com"); err != nil {
		fmt.Println("smtp rcpt error")
		return err
	}

	// Data
	wd, err := c.Data()
	if err != nil {
		fmt.Println("smtp data error")
		return err
	}

	_, err = wd.Write(m.Bytes())
	if err != nil {
		fmt.Println("smtp write error")
		return err
	}

	err = wd.Close()
	if err != nil {
		fmt.Println("smtp close error")
		return err
	}
	c.Quit()

	return nil
}

func main() {
	err := sendMail()
	if err != nil {
		panic(err)
	}
}