How to use
$ docker run -p 4180:4180 \
-e "HTTP_PORT=4180"
-e "UPSTREAM=127.0.0.1:8080" \
-e "CLIENT_ID=00000000000-000000000000000000000000000000000.apps.googleusercontent.com" \
-e "CLIENT_SECRET=XXXXXXXXXXXXXXXXXXXXX" \
-t mats116/oauth2_proxy