SOLID is a set of design principles from the world of object oriented programming that translate well to many languages.
Personally I had trouble initially understanding the Liskov Substitution Principle and its significance until I recently ran into a perfect example of what can go wrong when it is violated.
You can read all about it in this Issue on Github.
After publishing these findings, I submitted a PR to NewRelic's Go Agent to address the violation and they
agreed. The upstream PR was merged and documentation updated to discourage optional interface type casting
as a means of transaction retrieval.