The error message shows the wrong variable name, which might be confusing for new users.
There is a new handler coming up to fix #102 and I want to avoid falling into the classic Go trap of creating thousand-line functions.
This gets rid of the package called "server" and instead moves everything into the project root, such that Go actually builds us a binary called `nixery`. This is the first step towards factoring out CLI-based functionality for Nixery.
