Function spawn 

pub fn spawn<F>(future: F) -> JoinHandle<F::Output> 
where
    F: Future + Send + 'static,
    F::Output: Send + 'static,

Spawns a new asynchronous task with default options.

This is a convenience function for spawn_builder().

By default, the spawned task is attached to the current task in the task tree and will be cancelled if its parent exits, respecting the runtime’s OrphanPolicy.