You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: 19a-retry.go
    path of file: ./repos/gout/_example
    
    the code of the file until where you have to start completion: package main

import (
	"fmt"
	"github.com/guonaihong/gout"
	"github.com/guonaihong/gout/core"
	"time"
)

func main() {
	// 获取一个没有绑定服务的端口
	port := core.GetNoPortExists()
	err := gout.HEAD("127.0.0.1:" + port).
		Debug(true).                      //打开debug模式
		Filter().                         //打开过滤器.F
    
func main() {
	// 获取一个没有绑定服务的端口
	port := core.GetNoPortExists()
	err := gout.HEAD("127.0.0.1:" + port).
		Debug(true).                      //打开debug模式
		Filter().                         //打开过滤器.Filter()的简写是.F()
		Retry().                          //打开重试模式
		Attempt(5).                       //最多重试5次
		WaitTime(500 * time.Millisecond). //基本等待时间
		MaxWaitTime(3 * time.Second).     //最长等待时间
		Do()

	if err != nil {
		fmt.Printf("err = %v\n", err)
	}
}