Unable to change the directory structure with customLoader
## What happens?
I need to change the directory structure to module driven approach.

## Mini Showcase
**My Structure**
<img width="235" alt="Screenshot 2020-12-12 at 1 29 50 PM" src="https://user-images.githubusercontent.com/5563858/101979355-4a001f80-3c7e-11eb-91bc-856c77bf0572.png">
**My Config**
<img width="255" alt="Screenshot 2020-12-12 at 1 31 54 PM" src="https://user-images.githubusercontent.com/5563858/101979364-6d2acf00-3c7e-11eb-885a-12eed9f34568.png">
**My router.js**
```
const { controller } = app.blog;
router.get("/", .controller.home.index);
```
**What I Got**
`app.blog shows an empty object {}`

**Expected behavior**
controller & home object should be there to access index function.

## Context
- **Node Version**: v12.16.1
- **Egg Version**: ^2.15.1
- **Platform**: macOS Catalina 10.15.6
