A test to see if we can listen on IPv4 and IPv6 on the same port

dual-stack-ip-test.go

package main

import (
	"fmt"
	"net/http"
	"time"

	"github.com/labstack/echo/v4"
)

func ping(c echo.Context) error {
	return c.JSON(http.StatusOK, map[string]string{"message": "pong"})
}

func startServer(network, addr string) {
	srv := echo.New()
	srv.HideBanner = true
	srv.ListenerNetwork = network

	srv.GET("/ping", ping)

	err := srv.StartServer(&http.Server{
		Addr:              addr,
		ReadHeaderTimeout: 15 * time.Second,
	})
	if err != nil {
		panic(err)
	}
}

func queryServer(url string) {
	_, err := http.Get(url)
	if err == nil {
		fmt.Printf("%q is a success\n", url)
		return
	}

	fmt.Printf("%q fails\n", url)
}

func main() {
	go startServer("tcp6", "[::1]:8080")
	go startServer("tcp4", "127.0.0.1:8080")

	time.Sleep(100 * time.Millisecond)

	queryServer("http://127.0.0.1:8080/ping")
	queryServer("http://localhost:8080/ping")
	queryServer("http://[::1]:8080/ping")

	// "http://127.0.0.1:8080/ping" is a success
	// "http://localhost:8080/ping" is a success
	// "http://[::1]:8080/ping" is a success
}