Go, unlike Rails, is not a web/MVC framework. It's a systems language, which is even still separate and unique from Ruby, a dynamic language. I agree you'll certainly learn more from Go than you would from Rails, but it's helpful to be aware they're very different.

Apart from my own opinion of Rails (I'll pass, thanks), it's also worth considering that Go, again a systems language, may not always be appropriate for typical web development. That's not a rule by any means. Just pick the right tool for the job.