Error: listen EADDRINUSE: address already in use :::8989 at Server.setupListenHandle [as _listen2] (net.js:1279:14)

### Description

Error: listen EADDRINUSE: address already in use :::8989
at Server.setupListenHandle [as _listen2] (net.js:1279:14)

### Steps to reproduce

1. cd examlpes/sale
2.npm install
3. npm i webpack-cli@3.1.1 --save-dev
4. npm audit fix
5. npm run dev

### Plugin configration

```javascript
new SkeletonPlugin({
pathname: path.resolve(__dirname, `./shell`),
staticDir: path.resolve(__dirname, './dist'),
routes: ['/'],
// port: '6666',
loading: 'chiaroscuro',
svg: {
color: '#EFEFEF',
shape: 'circle',
shapeOpposite: ['.Rating-gray_1kpffd5_0 svg']
},
image: {
shape: 'rect', // `rect` | `circle`
color: '#EFEFEF',
shapeOpposite: ['.mint-swipe-items-wrap img']
},
pseudo: {
color: '#EFEFEF', // or transparent
shape: 'circle', // circle | rect
shapeOpposite: ['.delivery-icon-hollow_3q8_B5r_0', '.index-premium_39rl0v9']
},
button: {
color: '#EFEFEF',
excludes: ['.mint-swipe-items-wrap a']
},
defer: 5000,
excludes: [],
remove: [],
hide: ['.index-dashedline_7B79b3W', '.Rating-actived_GBtiHkB_0'],
grayBlock: ['#header'],
cssUnit: 'rem',
headless: true,
// minify: false,
cookies: [{
name: 'SID',
value: 'a495vvmEPEE4DZi083dr8yR3EAPYqW40HaWA',
url: 'https://h5.ele.me'
}, {
name: 'USERID',
value: '273745271',
url: 'https://h5.ele.me'
}],
noInfo: false
}),
```

### Versions

- Page Skeleton: ^0.10.12
- Webpack:4.41.5