import whenExit from 'when-exit';

onExit ( () => {
  console.log ( 'Callback 1' );
});

onExit ( () => {
  console.log ( 'Callback 2' );
});

const disposer = onExit ( () => {
  console.log ( 'Callback 3' );
});

disposer ();

process.exit (); // Callback 1 and 2 are called before exiting