A simple example of how to use async/await with hack-lang to perform non-blocking async tasks.

gistfile1.php

<?hh

async function helloAfter($name, $timeout) {
  // sleep asynchronously -- let other async functions do their job
  await SleepWaitHandle::create($timeout * 1000000);
  echo sprintf("hello %s\n", $name);
}

async function run() {
  $joe = helloAfter('Joe', 3);
  $mike = helloAfter('Mike', 1);
  // wait for both dependencies
  await GenArrayWaitHandle::create(array($joe, $mike));
}

run()->join();

// prints:
// hello Mike
// hello Joe


//The example is based on the discussion provided here: https://github.com/facebook/hhvm/issues/1494