Get the latest tech news
Go Upgrade Checklist
and how we upgraded 150+ services at once
Once we streamlined the process to what is described here today, 1.20 upgrade was completed in 3-4 weeks with almost no involvement from the service owners and no production issues. It is important to be prepared for unforeseen effects of language changes, which could delay the upgrade by weeks, months, or even indefinitely, depending on the desire for keeping true to the goals outlined above. The upgrade wasn't the responsible party here, the language kept backwards compatibility and regular sort was never intended to be stable.
Or read this on Hacker News