I like PHP. It's not overly complex to achieve what you want, you can write straight up HTML inside it, and I suppose I'm just used to it. I also like Go, having just discovered it while looking for something to write the back-end of a web app in that wasn't Node.js (can't abide callbacks everywhere).
I would like to be able to do most page generation in PHP because it's just what I'm comfortable doing for page generation, but I want the heavy lifting at the back to be done by Go. The back-end 'engine' needs to be able to do things like user-scheduled jobs to start with, but later extending to a web service endpoint and more, something I'd feel more comfortable doing in a compiled, statically typed language such as Go.
The only way I can think of allowing this to work is having all the PHP on an HTTP server and making REST or SOAP calls to the engine written in Go. Is this the only way to allow interoperability between the two languages or is there some other way?