I started gathering links for you, but it's easier just to provide the source of all the links: https://www.google.com/search?rls=en&q=github+postmortem&ie=...

Check out this talk: https://help.statuspage.io/knowledge_base/topics/postmortems

Take a look at these great collections: http://www.autopsy.io and https://www.cbinsights.com/blog/startup-failure-post-mortem/