POST / HTTP/1.1
Host: hoge.org
Content-Type: application/x-www-form-urlencoded

username=myid&password=mypw

//↑boiler plate↑
val pipe = (
  addHeader(Host("hoge.org"))
  ~> addHeader(`Content-Type`(`application/x-www-form-urlencoded`))
  ~> sendReceive.apply
)
pipe(Post("/")) onComplete {
  case Success(res) => println("okpk")
  case Failure(exc) => println(exc)
}