How to receive multicast from a docker image in a gitlab runner

I use a docker container launched in a gitlab-runner.
In this container, I’m not able to receive multicast.
When I run manually docker, through "docker run -d -it --net=host …, the docker is able to receive multicast.
But no multicast received when it is started on the gitlab-runner

I tried to configure the /etc/gitlab-runner/config.toml file :
network_mode = “host”,
but if I do that, I have errors in my gitlabci pipeline : “`unable to resolve host runner-Tqu_3sV …”

And I’m not sure to understand the section, from gitlab documentation.

Any idea?
Thank you!