// +build ignore

package main

import (
	"fmt"
	"log"
	"net"
	"net/http"
)

func main() {
	for _, host := range []string{"www.example.com", "www.google.com"} {
		inSeries(host)
		inParallel(host)
	}
}

func inSeries(host string) {
	fn := func(network, address string) (net.Conn, error) {
		c, err := net.Dial(network, address)
		if err == nil {
			log.Println("!", host, c.LocalAddr(), "->", c.RemoteAddr())
		}
		return c, err
	}
	addrs, err := net.LookupHost(host)
	if err != nil {
		log.Println("?", host, err)
		return
	}
	tr := &http.Transport{Dial: fn}
	client := http.Client{Transport: tr}
	for _, a := range addrs {
		resp, err := client.Get(fmt.Sprintf("http://%s/", net.JoinHostPort(a, "80")))
		if err != nil {
			log.Println("?", host, err)
			continue
		}
		log.Println(host, "connected to", resp.Request.URL.Host)
		resp.Body.Close()
	}
}

func inParallel(host string) {
	fn := func(network, address string) (net.Conn, error) {
		d := net.Dialer{DualStack: true}
		c, err := d.Dial(network, address)
		if err == nil {
			log.Println("!!", host, c.LocalAddr(), "->", c.RemoteAddr())
		}
		return c, err
	}
	tr := &http.Transport{Dial: fn}
	client := http.Client{Transport: tr}
	resp, err := client.Get(fmt.Sprintf("http://%s/", host))
	if err != nil {
		log.Println("??", host, err)
		return
	}
	log.Println(host, "connected to", resp.Request.URL.Host)
	resp.Body.Close()
}