Lua parse json value from request_body

Hello, i'm receiving POST to my lua endpoint.

That post body it's with json body.

I need to cut off one object from json post body

The body that is coming is looking like this :

{
    "param1": "1033893",
    "param2": "337483",
    "param3": "test",
    
}

I want to cut only param2 (only numbers) and put it as a value because I need to compare it with one file content

I'm using this local :
local check_body = ngx.req.get_body_data()

In bash script I normally run this :

echo $CURL_post_request | cut -d\| -f 1| grep -m1 -oP '\s*"param2"\s*:\s*\K[^,]+'| tr -d '"'| tr -d '}'

But in lua I'm not sure how I can fix this

Start with the mentioned ngx.req.get_body_data() entry point and review how this project handles JSON request bodies in Lua. Confirm how param2 can be obtained as a numeric value from the posted body and compared with file content; done means the extraction approach is documented or demonstrated clearly.