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**

**My Config**

**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