What are some unusual but useful Go libraries you've discovered?

Hey everyone! I'm always on the lookout for new and interesting Go libraries that might not be well-known but are incredibly useful. Recently, I stumbled upon go-cmp for easier comparisons in tests and color for adding color to console output, which have been game-changers for my projects. What are some of the lesser-known libraries you've discovered that you think more people should know about? Share your favorites and how you use them!