nodejs.JSONResponseFormatError: Unexpected token < in JSON at position 0
## What happens?
我请求一个API如果直接在浏览器请求返回的就是JSON格式。如果是用curl请求返回的就是HTML。而且提示错误`nodejs.JSONResponseFormatError: Unexpected token < in JSON at position 0`。
![WechatIMG2035](https://user-images.githubusercontent.com/11532418/97545175-8e549a80-1a05-11eb-9506-162034d734f6.jpeg)

![截屏2020-10-29 16 43 42](https://user-images.githubusercontent.com/11532418/97545414-f1dec800-1a05-11eb-82b1-dc1b7a5dcf09.png)

![截屏2020-10-29 16 44 28](https://user-images.githubusercontent.com/11532418/97545796-76c9e180-1a06-11eb-9586-211654e10152.png)


## Context
- **Node Version**: v12.18.3
- **Egg Version**: ^2.15.1
