How to send an email using Go (JP)?

Question

go

I need to send an email to @gmail. How can I do this on GO? Tried like this:

auth := smtp.PlainAuth("", "[email protected]", "....", "smtp.gmail.com")

  to := []string{"[email protected]"}
  msg := []byte("To: [email protected]\r\n" +
    "Subject: YES!\r\n" +
    "\r\n" +
    "This is the email body.\r\n")
  err := smtp.SendMail("smtp.gmail.com:587", auth, "[email protected]", to, msg)
  if err != nil {
    log.Fatal(err)
  }

But the error "unencrypted connection" crashes
And I did not find how to treat it