On my machine, I use rbenv to manage my Ruby environment. Occasionally, the required Ruby version for a project that I’m working on will be higher than what I have set up on my machine.
This results in having to upgrade my Ruby version. In order to do this, rbenv — specifically rbenv’s ruby-build plugin — will have to have the list of the latest Ruby versions before being able to download and set that up on your machine.
To update ruby-build simply cd into the folder with cd ~/.rbenv/plugins/ruby-build and pull the latest version by running git pull.
Once the pull request is complete, you should be able to run rbenv install -l and see a list of the latest Ruby versions available for you to install.