Best way to add a custom matcher function to Casdoor without forking the codebase?

we need to add a custom matcher https://casbin.org/docs/function#how-to-add-a-customized-function
what is the best way to add it to casdoor ? should I fork the code ? can I make it dynamically like plugin in go ?
(BTW we are using golang)

if fork needed can you point me to the right place in which I will call AddFunction("my_func", KeyMatchFunc)

you need to use casbin, why add to casdoor?