test.ex

defmodule TestApp.PageController do
  use Phoenix.Controller

  plug :action

  def test(conn, _params) do
    conn |> text "OK"
  end
end

test.go

package main

import (
	"fmt"
	"net/http"
)

func main() {
	http.HandleFunc("/test", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "OK")
	})
	http.ListenAndServe(":8080", nil)
}

test.hs

{-# LANGUAGE OverloadedStrings #-}

import Web.Scotty

main = scotty 3000 $ do
  get "/test" $ do
    html "OK"

test.rb

require 'sinatra'

get '/test' do
  'OK'
end