Docker install on Ubuntu via snap

It should be obvious but I discovered the hard way that you need to create the docker group prior to installing docker via snap if you want users to be able to run docker without using the sudo command.
All you need to do is
sudo addgroup --system docker
prior to
sudo snap install docker
then you can easily add any user (user) you want to run docker without sudo by issuing
sudo adduser user docker
if you have already installed the snap it looks like you need to remove and install again.