I've heard good things about the mongodb package and interface, but I haven't had a reason to use mongo.
So really if you use Go for your server side, you'll get a lot of nice benefits, listed by sambeau, but just be aware, you might have to tussle to find the right fit of backend tools, and you will likely have to make your own Model abstraction. This might not be a downside though, as I know a lot of engineers will build (or rebuild) the model layer no matter the framework.
I find gorp with Revel (http://robfig.github.io/revel/) makes for a powerful and performant backend. I just wish Revel had better testing integration.