How to apply plugin to sub-routes under a group route

[TheOrdinaryWow]

For example, I have

├── app.ts
├── routes
    ├── index.ts // index routes
    ├── posts
        ├── index.ts
        └── [id].ts // dynamic params

I want to apply a plugin to all routes under /post, like

• /post
• /post/:id

Where should I put the middleware?