failed to build as following the guide.

[johnsmithodom]

Describe the bug
A clear and concise description of what the bug is.
failed to build as following the guide.

1. See error
   game@root:~/demo-progressive-web-app$ npm run start

demo-pwa@1.0.2 start /home/game/demo-progressive-web-app
npm run css && node server.js

demo-pwa@1.0.2 css /home/game/demo-progressive-web-app
postcss -u autoprefixer -r css/*

events.js:377
throw er; // Unhandled 'error' event
^

Error: listen EADDRINUSE: address already in use :::3000
at Server.setupListenHandle [as _listen2] (net.js:1331:16)
at listenInCluster (net.js:1379:12)
at Server.listen (net.js:1465:7)
at Function.listen (/home/game/demo-progressive-web-app/node_modules/express/lib/application.js:635:24)
at Object. (/home/game/demo-progressive-web-app/server.js:51:5)
at Module._compile (internal/modules/cjs/loader.js:1114:14)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:1143:10)
at Module.load (internal/modules/cjs/loader.js:979:32)
at Function.Module._load (internal/modules/cjs/loader.js:819:12)
at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:75:12)
Emitted 'error' event on Server instance at:
at emitErrorNT (net.js:1358:8)
at processTicksAndRejections (internal/process/task_queues.js:82:21) {
code: 'EADDRINUSE',
errno: -98,
syscall: 'listen',
address: '::',
port: 3000
}
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! demo-pwa@1.0.2 start: npm run css && node server.js
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the demo-pwa@1.0.2 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! /home/game/.npm/_logs/2023-07-12T04_35_33_334Z-debug.log

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
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Desktop (please complete the following information):

• OS: [e.g. iOS]
  No LSB modules are available.
  Distributor ID: Debian
  Description: Debian GNU/Linux 11 (bullseye)
  Release: 11
  Codename: bullseye

game@root:/demo-progressive-web-app$ npm -v
6.14.18
game@root:/demo-progressive-web-app$ node -v
v14.21.3

• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.