Thread-safety

[eliank]

I was looking into expanding our API logging when I stumbled upon this Gem. When exploring its inner workings I found an issue with your middleware, it is not thread-safe because instance variables are used and passed whilst the middleware is used in a concurrent manner. See:
https://github.com/aserafin/grape_logging/blob/6e562a278864a382bf5cf37cda7bad8924f0ad29/lib/grape_logging/middleware/request_logger.rb#L60C34-L60C38

The @env can be overwritten during the call! causing the request and responds to mismatch, effectively sending a response that was meant for another client.

You could add this disclaimer to the readme, patch it or yank the gem altogether as it seems to no longer be maintained. Since I am not a user I won't be submitting a PR to fix it, but thank you for creating the gem regardless, its a nice insight to see how you solved it.