Change Token Parameter

I’m looking at trying to make a custom token for an application. It requires some hardcoded parameters, which I’m struggling to replicate. One of them is the “expiry:” token. The client scope generates an “exp:” field, but I’d like to change the name, or at least duplicate it with the “expiry:” name instead. Whats the best way to do this?

The easiest way is to convince the app to follow the standards [1]. I believe, in this case, it makes no sense to reinvent the wheel.

[1] RFC 7519 - JSON Web Token (JWT)