Function waker_fn 

pub fn waker_fn<F>(f: F) -> Waker
where
    F: Fn() + Send + Sync + 'static,

🔬This is a nightly-only experimental API. (waker_fn)

Converts a closure into a Waker.

The closure gets called every time the waker is woken.

Examples

#![feature(waker_fn)]
use std::task::waker_fn;

let waker = waker_fn(|| println!("woken"));

waker.wake_by_ref(); // Prints "woken".
waker.wake();        // Prints "woken".