The docker container for OSG Frontier Squid can be found here. The container allows the service to be configured either with the direct configuration file /etc/squid/squid.conf or with the more portable costumization script /etc/squid/customize.sh.
The Dockerfile uses the latest CentOS 7 version as the baseline image. We add the epel-release and the OSG software image (in this case release 3.4 for EL7). We then expose the port and import the entrypoint script, which will take care of configuring and running the service.