A Dockerfile that is used on fastlane's CIs which is configured for Ruby 2.7, Python 3.6.8, and Java 8.
This is built to be used on a CI (primarly CircleCI) when needing to either test fastlane on a Linux CI or test and deploy fastlane docs using Linux. Using this Dockerfile is the most effecient way of using the required Ruby, Python, and Java versions for each build and keeping it consistent.
docker build -t fastlanetools/ci:x.y.z ./
docker push fastlanetools/ci:x.y.z