Compare that to a language like Python or Ruby, where you need something "extra" to make it easier to do a web application. You could certainly do with just the standard library in other languages, but very few would choose that option, because it would involve write a lot of additional code.
I think it fair to include Go, because it's a language/programming environment, that comes with it's one built in web framework. A framework that's actually advanced enough that many don't need to look else where.
I know there should be some overhead when using a framework, but sometimes the cost is too high and it's useful to know it (compare php and symfony2, for example).
You can look at the Revel benchmark, a web framework written in Go which did quite well in the benchmark.