even if I go to drone-server container - I’m able to ping gitea server
the Drone server does not clone the repository. Drone spawns a per-pipeline container that is used to clone the repository. It essentially looks like this:
docker run -e DRONE_COMMIT=xxxx -e DRONE_BRANCH=yyyy drone/git
the clone step is just another step in your pipeline container. Each pipeline container is part of a per-container user-defined network. The gogs and drone server are on a separate bridge network in your configuration, and therefore, the user-defined network cannot resolve the gogs hostname.
this is a thread about clone issues with Gitea. If you are having clone problems in GitHub you should either find a thread related to GitHub, or you should create a new thread and you should provide more details (exact error message, you server configuration, your runner configuration, etc).