Monitor musicplayer actor and stop main process when actor stops

src/musicplayer.gleam

@@ -8,13 +8,14 @@ import musicplayer/ui/ui
 
 pub fn main() -> Nil {
   let input_keys_name: Name(Key) = process.new_name("input_keys")
-
   input.new(input_keys_name)
 
   let assert Ok(ui) = ui.new()
   let assert Ok(mpv) = mpv.new()
+  let assert Ok(musicplayer_pid) = musicplayer.new(ui, mpv, input_keys_name)
 
-  let exit = process.new_subject()
-  let assert Ok(_) = musicplayer.new(ui, mpv, input_keys_name, exit)
-  process.receive_forever(exit)
+  let monitor = process.monitor(musicplayer_pid)
+  process.new_selector()
+  |> process.select_specific_monitor(monitor, fn(_) { Nil })
+  |> process.selector_receive_forever
 }