Return a free port available in a range of provided ports.

check_port.go

package main

import (
	"errors"
	"fmt"
	"net"
	"strconv"
)

const (
	start = 8084
	end   = start + 10
)

func main() {
	availablePort, err := getFreePort()

	if err != nil {
		fmt.Printf("error: %v", err)
		return
	}
	fmt.Printf("using port: %v", availablePort)
}

func getFreePort() (int, error) {
	for port := start; port < end; port++ {
		listener, err := net.Listen("tcp", ":"+strconv.Itoa(port))

		if err == nil {
			listener.Close()
			return port, nil
		}
	}
	return 0, errors.New("no port available")
}