smpt.sendmail thow x509: certificate signed by unknown authority on windows - go

Question

I try send mail using smtp package on windows host, but I got this error "x509: certificate signed by unknown authority".
Certificate that using mail server is valid.
How can I understand that this is due to the fact that the certificate store is configured incorrectly.
But I didn't find any information on how to do it.
package main
import (
"crypto/tls"
"fmt"
"log"
"net"
"net/mail"
"net/smtp"
)
// StartTLS Email Example
func main() {
from := mail.Address{"", "examplt#email.com"}
to := mail.Address{"", "alhaos#gmail.com"}
subj := "This is the email subject"
body := "This is an example body.\n With two lines."
// Setup headers
headers := make(map[string]string)
headers["From"] = from.String()
headers["To"] = to.String()
headers["Subject"] = subj
// Setup message
message := ""
for k, v := range headers {
message += fmt.Sprintf("%s: %s\r\n", k, v)
}
message += "\r\n" + body
// Connect to the SMTP Server
servername := "MyServer:587"
host, _, _ := net.SplitHostPort(servername)
auth := smtp.PlainAuth("", "username", "pass", host)
// TLS config
tlsconfig := &tls.Config{
// InsecureSkipVerify: true,
ServerName: host,
}
c, err := smtp.Dial(servername)
if err != nil {
log.Panic(err)
}
c.StartTLS(tlsconfig)
// Auth
if err = c.Auth(auth); err != nil {
log.Panic(err)
}
// To && From
if err = c.Mail(from.Address); err != nil {
log.Panic(err)
}
if err = c.Rcpt(to.Address); err != nil {
log.Panic(err)
}
// Data
w, err := c.Data()
if err != nil {
log.Panic(err)
}
_, err = w.Write([]byte(message))
if err != nil {
log.Panic(err)
}
err = w.Close()
if err != nil {
log.Panic(err)
}
c.Quit()
}