[question] Can we use Timer::add(0, $func, $vars, false) to run tasks async

Hi,
I have seen that in other frameworks, in reality is the base of async.

`Timer::add(0, $func, $vars, false);`
Theoretically this task will be included to schedule in the event loop.
If so, perhaps it will be better to add a `Timer::once(0, $func, $vars);`.

Example:
`Timer::add(0, $send_mail, $vars, false);`

What do you think @walkor ??