How to configure Iron to listen to a Unix Domain Socket?

Question

I have this simple example from ironframework.io:

extern crate iron;

use iron::prelude::*;
use iron::status;

fn main() {
    fn hello_world(_: &mut Request) -> IronResult<Response> {
        Ok(Response::with((status::Ok, "Hello World!")))
    }
    // below code
    let _server = Iron::new(hello_world).http("localhost:3000").unwrap(); 
    println!("On 3000");
}

I want the server to listen a Unix Domain Socket (UDS).