$ go env
GO111MODULE='on'
GOARCH='amd64'
GOBIN='/home/ms/go/bin'
GOCACHE='/home/ms/.cache/go-build'
GOENV='/home/ms/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/ms/go/pkg/mod'
GONOPROXY='git.sr.ht'
GONOSUMDB='git.sr.ht'
GOOS='linux'
GOPATH='/home/ms/go'
GOPRIVATE='git.sr.ht'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/ms/opt/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/ms/opt/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='devel go1.21-a618094c2a Sat Jul 8 13:45:19 2023 +0700'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='0'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build721925861=/tmp/go-build -gno-record-gcc-switches'

package main
import (

"fmt"

"log"

"os"
"github.com/shuLhan/share/lib/email"
"github.com/shuLhan/share/lib/smtp"

)
func main() {

// Set up authentication information.

var (

smtpUser       = os.Getenv(SMTP_USER)

smtpPass       = os.Getenv(SMTP_PASS)

smtpServer     = os.Getenv(SMTP_SERVER)

smtpServerPort = os.Getenv(SMTP_SERVER_PORT)

from           = os.Getenv(SMTP_FROM)

to             = os.Getenv(SMTP_TO)

)
fmt.Printf("SMTP user: %s\n", smtpUser)
fmt.Printf("SMTP pass: %s\n", smtpPass)
fmt.Printf("SMTP addr: %s:%s\n", smtpServer, smtpServerPort)
fmt.Printf("From     : %s\n", from)
fmt.Printf("To       : %s\n", to)

var (
	subject  = `Truncated message`
	bodyText = "A line that precisely have length 75 with . + LF will cause DATA truncation.\n" +
		"\n" +
		"This line will not be received.\n"

	msg    email.Message
	mailtx *smtp.MailTx
	data   []byte
	err    error
)

err = msg.SetFrom(from)
if err != nil {
	log.Fatal(err)
}
err = msg.SetTo(to)
if err != nil {
	log.Fatal(err)
}
msg.SetSubject(subject)
err = msg.SetBodyText([]byte(bodyText))
if err != nil {
	log.Fatal(err)
}
data, err = msg.Pack()
if err != nil {
	log.Fatal(err)
}

fmt.Printf("Data: %s\n", data)

mailtx = smtp.NewMailTx(from, []string{to}, data)

var (
	clientOpts = smtp.ClientOptions{
		ServerUrl:     fmt.Sprintf(`smtps://%s:%s`, smtpServer, smtpServerPort),
		AuthUser:      smtpUser,
		AuthPass:      smtpPass,
		AuthMechanism: smtp.SaslMechanismPlain,
	}
	cl *smtp.Client
)

cl, err = smtp.NewClient(clientOpts)
if err != nil {
	log.Fatal(err)
}

res, err := cl.MailTx(mailtx)
if err != nil {
	log.Fatal(`MailTx:`, err)
}

log.Printf(`MailTx: response: %+v`, res)

_, err = cl.Quit()
if err != nil {
	log.Fatal(err)
}

}