gulp 4.0.2 auto reload server watch files

gulpfile.babel.js

// base on this links
// https://gist.github.com/webdesserts/5632955

// need this for "gulp default" to run command line
// @babel/register 

import { src, dest, watch, parallel, series } from "gulp";
import {spawn} from "child_process";

import config from'./config';
//import babel from "gulp-babel";
//import uglify from 'gulp-uglify';
//import buffer from 'vinyl-buffer';
//import size from 'gulp-size';

let node;

//BASIC ACCESS
const src_client_files=[
  './src/client.js'
];

//web public host
const output_dest='public';

// CLIENT BUILD
function client_build(callback){
  // task
  return src(src_client_files)
    //.pipe(buffer())
    //.pipe(uglify())
    //.pipe(size())
    .pipe(dest(output_dest));
  //cb();
}
exports.client_build = client_build;

//WATCH FILES
function watchFiles(callback) {
  //file change update
  watch(src_client_files, client_build);

  //watch all file changes to restart server
  watch(['./src/**/*.js'], function() {
    reload_server();
  });

  callback();
}
exports.watchFiles = watchFiles;

// https://gist.github.com/webdesserts/5632955
//nodejs functions
function reload_server(callback) {
  if (node) node.kill();
  let serverfile='./appserver.js';
  node = spawn('node', [serverfile], {stdio: 'inherit'});
  node.on('close', function (code) {
    if (code === 8) {
      gulp.log('Error detected, waiting for changes...');
    }
  });
  //return callback();
}
exports.reload_server = reload_server;

//EXPORT DEFAULT
exports.default = series(
  client_build
  , watchFiles
  , reload_server
);

// clean up if an error goes unhandled.
process.on('exit', function() {
  if (node) node.kill()
});

package.json

{
  "name": "gulpreload",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@babel/core": "^7.15.8",
    "@babel/node": "^7.15.8",
    "@babel/preset-env": "^7.15.8",
    "@babel/register": "^7.15.3",
    "fastify": "^3.22.1",
    "fastify-static": "^4.4.2",
    "gulp": "^4.0.2"
  }
}