Testing GetFreePort concurrent allocation with 1000 goroutines

test_portalloc.go

package main

import (
	"fmt"
	"net"
	"sync"
)

func GetFreePort() (int, error) {
	addr, err := net.ResolveTCPAddr("tcp", "localhost:0")
	if err != nil {
		return 0, err
	}

	l, err := net.ListenTCP("tcp", addr)
	if err != nil {
		return 0, err
	}
	defer l.Close()
	return l.Addr().(*net.TCPAddr).Port, nil
}

func allocatePorts(wg *sync.WaitGroup, maxAllocs int) {
	wg.Add(1)
	errors := 0
	for i := 0; i < maxAllocs; i++ {
		_, err := GetFreePort()
		if err != nil {
			fmt.Println("Got error", err)
			errors++
		}
	}
	if errors > 0 {
		fmt.Printf("Got %d errors out of %d allocation attempts", errors, maxAllocs)
	}
	wg.Done()
}

func main() {
	var wg sync.WaitGroup
	maxAllocs := 1000
	maxGoroutines := 1000
	for i := 0; i < maxGoroutines; i++ {
		go allocatePorts(&wg, maxAllocs)
	}
	wg.Wait()
}