Yes it does. We (at the Netherlands eScience Center) will be building such an interface next January, extending Entangled (https://entangled.github.io). This approach uses Markdown and enables editing your code both in Markdown and generated source codes, synchronizing when files are written to. Currently with traditional documentation site generators like MkDocs, you can get nicely presented content, but what you suggest requires a bit more work. We will build better content navigation in Pandoc, and a side-by-side view as you suggest is definitely on the table. Also: outside contributions are more than welcome ;)

It does look nifty. Altho getting up to speed is non-trivial. I don't suppose you have any working examples in the Go language ?

Sadly nothing Go specific. We're working on making it easier to work with.

Go already has built-in support for tests and for executable examples (that go into generated package documentation), so it might get hairy.