Dev json engine

[ChenPuChu]

• Implemented a user-customizable JSON render function
  • This function does not disrupt the implementation of the original function
  • This function is implemented through the factory mode
  • This is my first time submitting a fix. Maybe my code is not standard. If there is anything wrong, please feel free to correct me.

Fixes #4094

[ChenPuChu]

@JimChenWYU

[JimChenWYU]

I don't know your pr how to fix his problem. In my understood, he just want to change response body in his gin-middleware

[manuelarte]

@JimChenWYU thanks for answering. To be more clear, what I want is that, when modifying the response, I want to keep the same "format" the user used.

So, my middleware can't know whether the user used c.indentedjson, or c.json to format the output

[ChenPuChu]

@manuelarte Okay, this is your guideline

[manuelarte]

So, in my middleware function, what would I need to write to retrieve what render was used?