https://medium.com/@nielssj/docker-volumes-and-file-system-permissions-772c1aee23ca
In short,
Set group ownership of the directory to be used as volume to some GID (in this example 1024) not used on any actual groups on the host
chown :1024 /data/myvolumeChange permissions on the directory to give full access to members of the group (read+write+execute)
chmod 775 /data/myvolumeEnsure all future content in the folder will inherit group ownership
chmod g+s /data/myvolume