outlet-mapping.scala

  val bcMappingFlow = Flow.fromGraph(GraphDSL.create() { implicit b =>
    import GraphDSL.Implicits._
    val bc = b.add(Broadcast[Int](2))
    val printSink = Sink.foreach(println)
    bc.out(1).map(i => i * 2) ~> printSink
    FlowShape(bc.in, bc.out(0))
  })

  Source(1 to 10)
    .via(bcMappingFlow)
    .runForeach(n => println("runForeach, received: " + n))