package main

import (
	"fmt"
	"io/ioutil"
	"net"
	"os"
	"strings"
	"sync"
	"time"
)

func fdCount() int {
	buf, err := ioutil.ReadFile(fmt.Sprintf("/proc/%v/fd", os.Getpid()))
	if err != nil {
		panic(err)
	}
	return strings.Count(string(buf), "/net/tcp/")
}

func main() {
	fmt.Printf("fd count before: %v\n", fdCount())

	var wg sync.WaitGroup
	for i := 0; i < 100; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			c, err := net.DialTimeout("tcp", "8.8.8.8:1234", 5*time.Second)
			if err != nil {
				fmt.Printf("%v\n", err)
				return
			}
			c.Close()
		}()
	}
	wg.Wait()

	fmt.Printf("fd count after: %v\n", fdCount())
	time.Sleep(time.Hour)
}