port.go

port.go

// Package port allows to obtain a free port that is ready to use.
package port

import (
	"net"

	"emperror.dev/errors"
)

// New returns a free open port that is ready to use.
func New() (int, error) {
	addr, err := net.ResolveTCPAddr("tcp", "127.0.0.1:0")
	if err != nil {
		return 0, errors.WithStack(err)
	}

	l, err := net.ListenTCP("tcp", addr)
	if err != nil {
		return 0, errors.WithStack(err)
	}
	defer l.Close() //nolint:errcheck

	return l.Addr().(*net.TCPAddr).Port, nil
}