NetworkComponent.scala

  type Transaction = mutable.Builder[Any, _]

  def transaction[R](fn: Transaction => R): Future[NetworkSession] = {
    val buf = List.newBuilder[Any]
    fn(buf)

    @tailrec
    def rec(fut: Future[NetworkSession], buf: List[Any]): Future[NetworkSession] = buf match {
      case head :: tail => rec(fut.flatMap(_.write(head)), tail)
      case Nil => fut
    }

    rec(Future(this), buf.result()).flatMap(_.flush())
  }