Rails is opinionated, yes, but I'm generally pretty satisfied with their opinions, and it's nice to have a full Batteries-included package.
Later I started use just standard library with http://www.gorillatoolkit.org and used fswatch for hot reload. Now there are lot of alternative in routers but no clear winner.(and thats good thing) I will suggest go with standard library and simple router but be ready to revert back to framework like revel if that doesn't workout.
As far as application structure, I'm not really sure what you mean. Go projects are divided into packages which can be any number of files. At some point you'll have a main package which has a main() function which gets called to start your server. It's similar to C, for example.
That said, the variety can also be a plus. Some people chose to use something like Martini that does dependency injection. Others think that's not a great idea.