How to run application server with local(forked) Chirpstack API?

I run Chirpstack gw bridge, network server and application server on local. I forked them all and make some changes. Now I need to customize the Chirpstack API.
I can make changes in API by editing .proto files but i can not integrate the API with application server. How can I comunicate and run local Chirpstack API with my local Application Server ?

It is not clear or its not showing what should exactly do but it helps:

After hours of searching(I am a newbie in go) there is a small piece of replace command as commented in the bottom of the Aplication Server’s go.mod file.
You can use your local api by uncommenting this line:

replace => …/chirpstack-api/go

Also I added this line to the GW and NS’s go.mod files to use the same api on these servers.