Update GoUsers.md adding Mentorink as a user of Go

Author: mkafkas

GoUsers.md

@@ -1389,6 +1389,7 @@ Certificate Expiry Monitor Controller monitors the expiration of TLS certificate
   * [iZettle](https://www.izettle.com/gb) - [github](https://github.com/iZettle/)
   * [Logit.io](https://logit.io/)
   * [Lush Digital](http://careers.lush.com/) - [GitHub](https://github.com/lushdigital/)
+  * [Mentorink](https://www.mentorink.com/) - [GitHub](https://github.com/mentorink/)
   * [Micro](https://micro.mu/) - [github](https://github.com/micro)
   * [Monzo](https://monzo.com/) - [github](https://github.com/monzo), [blog](https://monzo.com/blog/2016/09/19/building-a-modern-bank-backend/)
   * [New Bamboo](http://www.new-bamboo.co.uk) - [blog](http://blog.new-bamboo.co.uk/2013/09/17/micro-network-daemons-in-go)