[egg-bin]自身单元测试有18个失败的case，有解决的方案吗
## What happens?

[egg-bin]自身单元测试有18个失败的case:
```shell
➜  egg-bin-4.15.0 yarn test-local
yarn run v1.22.10
$ node bin/egg-bin.js test -t 3600000


  test/lib/cmd/debug.test.js
    real egg
      1) should proxy
      2) should proxy with port

  test/lib/cmd/test.test.js
    simplify mocha error stack
      3) should clean co error stack
      4) should clean callback error stack

  test/ts.test.js
    5) should support ts
    ✓ should support ts test (1133ms)
    real application
      6) should start app
      7) should test app
      8) should cov app
      9) should cov app in cluster mod
    error stacks
      10) should correct error stack line number in starting app
      11) should correct error stack line number in testing app
      12) should correct error stack line number in covering app
    egg.typescript = true
      13) should start app
      14) should fail start app with --no-ts
      15) should test app
      16) should cov app
    egg.declarations = true
      17) should load egg-ts-helper with dts flag
      18) should load egg-ts-helper with egg.declarations = true
```
看了一下错误信息，都是`coffee`这个包抛出的：
![image](https://user-images.githubusercontent.com/10141527/113805047-53177e00-9792-11eb-972f-f57ba6cb7ef6.png)

## 复现步骤，错误日志以及相关配置

1. `yarn` 安装依赖
2. `yarn test-local` 运行本地单元测试

## 相关环境信息
- **操作系统**：macOS Big Sur 11.2.3
- **Node 版本**：v14.16.0
- **yarn 版本**：v1.22.10
- **Egg 版本**：^2.20.2
- **egg-bin版本**: 4.15.0
