how to add a user to docker group if docker group is there?

Archives Ansible Project
1

default user add to users group, if docker group is there, also add to docker group.

How to write this snabile-playbook?

2

This may be of some help for you. https://github.com/mrlesmithjr/ansible-docker/blob/master/tasks/users.yml

Basically this should work for you as a playbook.