AsyncWait.hs

import Control.Concurrent
import Control.Concurrent.Async
import System.Random

delayedOutput :: String -> IO ()
delayedOutput m = do
  gen <- newStdGen
  let (t, _) = randomR (1, 10) ge
  -- delay in microseconds
  threadDelay (t * 1000000)
  -- display message
  putStrLn m
  return ()

main :: IO ()
main = do
  putStrLn "Fight!"
  a <- async (delayedOutput "Finish him!")
  wait a
  return ()