DeprecationWarning: Use of deprecated folder mapping "./" in the "exports" field
node: `v16.13.0`

```
DeprecationWarning: Use of deprecated folder mapping "./" in the "exports" field module resolution of the package at `node_modules/koa/package.json.`
```

This is only a warning issued by "nodejs". It is recommended to make corrections according to the warning, because some writing methods are not recommended.