golang：send mail using smtp package

go语言发送邮件，可以使用smtp包，两个关键函数：

func PlainAuth(identity, username, password, host string) Auth

func SendMail(addr string, a Auth, from string, to []string, msg []byte) error

刚开始玩的时候，很好奇邮件的title是怎么设置进去的，毕竟从代码没看见有setTitle。后来发现是解析msg获取标题、发件人、收件人、邮件格式、邮件内容等；因此msg需要按一定格式写：To: xxx\r\nFrom:xxxx\r\nSubject: xxxx\r\nContent-Type:text/html; charset=UTF-8\r\n\r\n[邮件内容]

func (this *TestController) SendMail(){

    subject := "This is golang test email..."
    user := "xxxxx@163.com"
    to := []string {"xxxxx@163.com"}
    nickname := "dyao"
    content := "mail body....."
    contentType := "Content-Type: text/html; charset=UTF-8"
    msg := []byte("To: " + strings.Join(to, ",") + "\r\nFrom: " + nickname + "<" + user + ">\r\nSubject: " + subject + "\r\n" + contentType + "\r\n\r\n" + content)

    auth := smtp.PlainAuth(
        "",
        user,
        "testpassword",
        "smtp.163.com",
    )

    err := smtp.SendMail(
        "smtp.163.com:25",
        auth,
        user,
        to,
        []byte(msg),
    )
    if err != nil{
        log.Fatal(err)
    }else {
        log.Printf("Mail send:\r\n%s", msg)
    }
}

===================2018/01/18=======================

163邮箱，把发送的邮件当垃圾拦截了，今天打算换qq邮箱，被坑到怀疑人生....

密码，不是qq登陆密码，是授权码！授权码！授权码！授权码！

授权码，在qq邮箱设置里面获取，会发送到手机上