Added go-simple-mail (#2738)

README.md

@@ -601,6 +601,7 @@ Please take a quick gander at the [contribution guidelines](https://github.com/a
 * [go-imap](https://github.com/emersion/go-imap) - IMAP library for clients and servers.
 * [go-message](https://github.com/emersion/go-message) - Streaming library for the Internet Message Format and mail messages.
 * [go-premailer](https://github.com/vanng822/go-premailer) - Inline styling for HTML mail in Go.
+* [go-simple-mail](https://github.com/xhit/go-simple-mail) - Very simple package to send emails with SMTP Keep Alive and two timeouts: Connect and Send.
 * [Gomail](https://github.com/go-gomail/gomail/) - Gomail is a very simple and powerful package to send emails.
 * [Hectane](https://github.com/hectane/hectane) - Lightweight SMTP client providing an HTTP API.
 * [hermes](https://github.com/matcornic/hermes) - Golang package that generates clean, responsive HTML e-mails.