What unusual or non-standard packages have you used in your practice?

In my practice with Go, I have used several non-standard packages that are not part of the standard library but significantly simplify tasks:

• github.com/spf13/viper — for flexible configuration management.
• github.com/olekukonko/tablewriter — for beautiful table output in the console.
• github.com/fatih/color — for colored terminal output formatting.
• golang.org/x/crypto — for advanced cryptographic functions.

These packages help quickly implement a user-friendly and functional interface or add specific capabilities without inventing a custom solution.