pool14.scala

val ae = IO.async[Unit] { cb =>
  ec3.submit(new Runnable {
    override def run(): Unit = {
      println(Thread.currentThread().getName + " (async)")
      cb(Left(new IllegalStateException()))
    }
  })
}

run("async error") {
  ae.guarantee(printThread)
}

/*
Outputs:

-- async error --
ec3-1-785992331 (async)
ec3-1-785992331
*/