If you are running a docker container and if you need to access a service running on the host for testing, the option in Ubuntu and other linux distros is to use the docker0 interface. This will not work in MacOS as Docker-Desktop-for-Mac networking is programmed different.
To make this scenario work, Docker Desktop for Mac provides a work around and it is pretty simple. The gateway is provided with an internal DNS name
host.docker.internal. This resolves to the host’s volatile internal IP. Docker also provides an alternate
gateway.docker.internal DNS name to access the host from containers.
More info is available at Docker For Mac documentation