tencent cloud

package main
import (
    "bytes"
    "crypto/tls"
    "encoding/base64"
    "fmt"
    "io/ioutil"
    "log"
    "mime"
    "net"
    "net/smtp"
    "time"
)

// Test465Attachment  for port 465
func Test465Attachment() error {
    boundary := "GoBoundary"
    host := "sg-smtp.qcloudmail.com"
    port := 465
    email := "abc@cd.com"
    password := "***"
    toEmail := "test@test123.com"
    header := make(map[string]string)
    header["From"] = "test " + "<" + email + ">"
    header["To"] = toEmail
    header["Subject"] = "Test465Attachment"
    header["Content-Type"] = "multipart/mixed;boundary=" + boundary
    // This field is not used for the time being. Pass in `1.0` by default
    header["Mime-Version"] = "1.0"
    // This field is not used for the time being
    header["Date"] = time.Now().String()
    bodyHtml := "\n\n\n<meta charset="\"utf-8\"">\n<title>hello world</title>\n\n\n " +
        "<h1>My first heading</h1>\n    <p>My first paragraph.</p>\n\n"
    message := ""
    for k, v := range header {
        message += fmt.Sprintf("%s: %s\r\n", k, v)
    }
    buffer := bytes.NewBuffer(nil)
    buffer.WriteString(message)
    contentType := "Content-Type: text/html" + "; charset=UTF-8"
    body := "\r\n--" + boundary + "\r\n"
    body += "Content-Type:" + contentType + "\r\n"
    body += "\r\n" + bodyHtml + "\r\n"
    buffer.WriteString(body)

    attachment := "\r\n--" + boundary + "\r\n"
    attachment += "Content-Transfer-Encoding:base64\r\n"
    attachment += "Content-Disposition:attachment\r\n"
    attachment += "Content-Type:" + "application/octet-stream" + ";name=\"" + mime.BEncoding.Encode("UTF-8",
        "./go.mod") + "\"\r\n"
    buffer.WriteString(attachment)
    writeFile(buffer, "./go.mod")
    // Multiple attachments can be spliced at the end. There can be 10 attachments at most, each of which cannot exceed 5 MB in size. The TOTAL size of all attachments cannot exceed 8–9 MB; otherwise, EOF will be returned
    attachment1 := "\r\n--" + boundary + "\r\n"
    attachment1 += "Content-Transfer-Encoding:base64\r\n"
    attachment1 += "Content-Disposition:attachment\r\n"
    attachment1 += "Content-Type:" + "application/octet-stream" + ";name=\"" + mime.BEncoding.Encode("UTF-8",
        "./bbbb.txt") + "\"\r\n"
    buffer.WriteString(attachment1)
    writeFile(buffer, "./bbbb.txt")
    defer func() {
        if err := recover(); err != nil {
            log.Fatalln(err)
        }
    }()
    
    buffer.WriteString("\r\n--" + boundary + "--")
    message += "\r\n" + body
    auth := smtp.PlainAuth(
        "",
        email,
        password,
        host,
    )
    err := SendMailWithTLS(
        fmt.Sprintf("%s:%d", host, port),
        auth,
        email,
        []string{toEmail},
        buffer.Bytes(),
    )
    if err != nil {
        fmt.Println("Send email error:", err)
    } else {
        fmt.Println("Send mail success!")
    }
    return err
}

// Dial return a smtp client
func Dial(addr string) (*smtp.Client, error) {
    conn, err := tls.Dial("tcp", addr, nil)
    if err != nil {
        log.Println("tls.Dial Error:", err)
        return nil, err
    }

    host, _, _ := net.SplitHostPort(addr)
    return smtp.NewClient(conn, host)
}

// SendMailWithTLS send email with tls
func SendMailWithTLS(addr string, auth smtp.Auth, from string,
    to []string, msg []byte) (err error) {
    //create smtp client
    c, err := Dial(addr)
    if err != nil {
        log.Println("Create smtp client error:", err)
        return err
    }
    defer c.Close()
    if auth != nil {
        if ok, _ := c.Extension("AUTH"); ok {
            if err = c.Auth(auth); err != nil {
                log.Println("Error during AUTH", err)
                return err
            }
        }
    }
    if err = c.Mail(from); err != nil {
        return err
    }
    for _, addr := range to {
        if err = c.Rcpt(addr); err != nil {
            return err
        }
    }
    w, err := c.Data()
    if err != nil {
        return err
    }
    _, err = w.Write(msg)
    if err != nil {
        return err
    }
    err = w.Close()
    if err != nil {
        return err
    }
    return c.Quit()
}

// writeFile read file to buffer
func writeFile(buffer *bytes.Buffer, fileName string) {
    file, err := ioutil.ReadFile(fileName)
    if err != nil {
        panic(err.Error())
    }
    payload := make([]byte, base64.StdEncoding.EncodedLen(len(file)))
    base64.StdEncoding.Encode(payload, file)
    buffer.WriteString("\r\n")
    for index, line := 0, len(payload); index < line; index++ {
        buffer.WriteByte(payload[index])
        if (index+1)%76 == 0 {
            buffer.WriteString("\r\n")
        }
    }
}

func main() {
    Test465Attachment()
}