While I completely agree that the standard library is all you need in quite a lot of cases, the parent seems to be asking from more of a "how do I structure my application" perspective. A tool that generates the boilerplate necessary to use the standard library effectively in a complete application. Not just http handlers, but think of the persistence layer, for example. The standard library does not assist much with the engineering aspect of the job.
I'm not trolling. It seriously is easy enough to crank out a basic web app in less than a hundred lines of code that runs very well with just the standard library.