Shutting down nickel server

[ruabmbua]

I hope this question is not silly.

How can I actually stop my nickel.rs web application. I mean how is it possible to make the
Nickel::listen method exit.
Cleaning up resources and running drop on things is very important in my application.

I already tried to just use std::process::exit(0); in my middleware, but of cource that does not clean up anything at all.