net.go

// Copyright 2015-present, Cyrill @ Schumacher.fm and the CoreStore contributors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package cstesting

import (
	"net"

	"github.com/corestoreio/errors"
)

// MustFreePort returns a free TCP port or panics on error.
func MustFreePort() int {
	addr, err := net.ResolveTCPAddr("tcp", "localhost:0")
	if err != nil {
		panic(err)
	}

	l, err := net.ListenTCP("tcp", addr)
	if err != nil {
		panic(err)
	}
	defer l.Close()
	if ta, ok := l.Addr().(*net.TCPAddr); ok {
		return ta.Port
	}
	panic(errors.NotSupported.Newf("[cstesting] Type %T does not type assert to *net.TCPAddr", l.Addr()))
}