error: called `map(f)` on an Option value where `f` is a unit closure
   --> src/scheduler.rs:278:5
    |
278 |        optional_display.as_mut().map(|display| {
    |   _____^
    |  |_____|
    | ||
279 | ||       display.start();
280 | ||       display.render();
281 | ||       let worker_ids: Vec<String> = (0..display_worker_count)
...   ||
287 | ||       }
288 | ||     });
    | ||______^- help: try this: `if let Some(display) = optional_display.as_mut() { ... }`
    | |_______|`