I am currently switching to Go from PHP. It's really not that hard to learn once you get your head around the static types and lack of OO - last thing is a big plus in my book. The way they handle it with structs and interfaces are so much better.
Biggest problem is there are limited ressources on the net about Go, and the documentation is lacking compared to PHP, examples are sparse. So be warned it will take you some time to learn.
But it's such a beautiful and simple language, that will be a breeze to support in the future for you and your team. Debugging and maintainability is top knotch.
For the frontend i recommend AngularJS