Articles on Go web frameworks all end up at the same conclusion. The Go standard library is so strong around web servers it's hard to recommend anything else.
The http packages provides the bare minimum. A serious app requires way more features than what is provided,a router than handles route variables, a middleware stack, a proper context, a proper session mechanism if one writes a website...
So it's normal people write their own libraries on top of it ( like mine @ gopkg.in/interactiv/expresso.v0 ,still alpha )