ioPar.scala

import $ivy.`org.typelevel::cats-core:1.0.1`
import $ivy.`org.typelevel::cats-effect:0.9`
import cats.effect.IO
import cats.implicits._

def f(s: String) = IO { Thread.sleep(1000); s }

def timeIO[A](f: IO[A]): A = {
    val start = System.nanoTime
    val result = f.unsafeRunSync()
    println(s"Time: ${System.nanoTime - start}")
    result
  }

timeIO((f("hi"), f("bye")).parMapN((a, b) => println(a,b))) // takes 2 seconds~

timeIO((f("1"), f("2"), f("3")).parMapN((a, b, c) => println(a,b, c))) // takes 3 seconds~