before_install:
  - gem install bundler
language: ruby
rvm:
  - '2.3'
  - '2.4'
  - '2.5'
  - '2.6'
  - '2.7'
  - ruby-head
matrix:
  allow_failures:
    - rvm: ruby-head
  fast_finish: true

before_install:
  - gem install bundler
language: ruby
rvm:
  - '2.4'
  - '2.5'
  - '2.6'
  - '2.7'
  - ruby-head
matrix:
  allow_failures:
    - rvm: ruby-head
  fast_finish: true

Support of Ruby 2.3 has ended
Support of Ruby 2.3 has ended

https://www.ruby-lang.org/en/news/2019/03/31/support-of-ruby-2-3-has-ended/
