reload daemon then http server can't listen on other port

[qianxiansheng90]

env:
Linux l-qfy0.dba.dev.cn0 3.10.0-327.28.3.el7.x86_64 #1 SMP Thu Aug 18 19:05:49 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

go version go1.17 linux/amd64

test.go

import (
	"context"
	"flag"
	"fmt"
	"os/exec"
	"strconv"
	"syscall"

	"github.com/fvbock/endless"
	"github.com/gin-gonic/gin"
)

var ctx context.Context
var cancel context.CancelFunc
var reload bool

var port = flag.Int("port", 8080, "")

func main() {
	flag.Parse()
	ListenHTTP(setReload)
}

func setReload() {
	reload = true
}
func ListenHTTP(reloadFunc func()) error {
	var handler = gin.Default()
	handler.GET("/", startDaemon())
	handler.GET("/hello", hello())

	ctx, cancel = context.WithCancel(context.Background())
	defer cancel()
	s := endless.NewServer(":"+strconv.Itoa(*port), handler)
	go func() {
		select {
		case <-ctx.Done():
		}
		if s != nil {
			if err := s.Shutdown(ctx); err != nil {
				fmt.Println(err)
			}
		}
	}()
	s.SignalHooks[endless.PRE_SIGNAL][syscall.SIGHUP] = append(
		s.SignalHooks[endless.PRE_SIGNAL][syscall.SIGHUP],
		reloadFunc)
	if err := s.ListenAndServe(); err != nil {
		return err
	}
	return nil
}
func hello() gin.HandlerFunc {
	return func(c *gin.Context) {
		fmt.Println("hello ", *port)
	}
}
func startDaemon() gin.HandlerFunc {
	return func(c *gin.Context) {
		start(c)
	}
}

func start(c *gin.Context) (err error) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	cmd := exec.CommandContext(ctx, "sh", []string{"start.sh"}...)
	err = cmd.Run()
	if err != nil {
		fmt.Println(err)
		return
	}
	return
}

start.sh

nohup /home/qfy/tmp/test --port=8081 > /dev/null 2>&1 &

basedir:/root/tmp

steps:

1. run test

2. start with new shell, then send http requst，now 8081 is listening

3. kill 8081 ，and reload test

4.then send http requst，but 8081 is not listening

Is that a bug need to fix ?
And how can I resolve it.