There's a few, but I think it's still too early to really call out a "defacto" framework.
Revel, as mentioned, is a popular "full stack" framework, but it can be pretty heavy. web.go[1] gets a lot of use (it sits at a Flask/Sinatra level), and beego[5] looks good but it's also totally acceptable to plug a few libraries together without much work on top.
For example, I'm using:
- mux, sessions, schema & context from Gorilla[2]
- go.auth for social sign-in [3]
- the RethinkDB driver [4]
... and that's about it. Write your routes with mux, set up your handlers with auth/sessions/schema, and generate your models & queries with whatever DB you want. The standard html/template library is good enough (and there's a Mustache library if you need it), and the standard http library covers everything in between.
TL;DR: If you enjoy writing Flask/Sinatra apps, you'll enjoy writing Go web apps. If you're coming from a full-stack framework (like me), there is definitely a learning curve, but I feel that Go's documentation and std. lib flatten that out a little.
It provides nearly everything, likely including things you don't even need. It's likely that a lot of the parts included won't be needed by a "typical" web application, and if you want to do things another way you'll need to spend some time switching those components out. To be fair though, having "everything" can be a big plus, especially when you don't know what you might need (or have the time to glue things together).
I don't know how tightly coupled the components are in Revel, but if it's like Django, some things are easy to add/remove (middleware), and others are much harder to work around (ORM, views, etc.).
Many of the people in the Go community are anti-framework and pro-library. (inversion of control; a library is provided code called by your code, versus a Framework provided code that calls your code).
That being said, right now the dominate Go web library is "net/http" from the Go standard library, supplemented by Gorilla (as needed): http://www.gorillatoolkit.org/
If what you are looking for is really a Go web framework however, there are a few in development including Revel: http://robfig.github.io/revel/
I've written a small production web project and several medium-sized personal projects in Go, and have not yet found a need for a web framework outside of net/http. I've used several libraries that work as nested/stacked handlers under net/http; Go's structure embedding is a natural fit for that.
I would love to know about this as well. Basically a basic rundown of how Go works in relation to running various web facing stuff (a simple API for example).
