Structured Logging in Go: A Complete Guide to slog in Go 1.21

Why slog Matters for Go Developers

For years, Go developers have debated structured logging. It consistently topped community surveys, and the ecosystem responded with dozens of solutions—from logrus (used in 100,000+ packages) to Zap. But here’s the problem: when you build large applications, you inevitably pull in multiple logging packages through dependencies. Each one has its own way of outputting logs, making it nearly impossible to maintain consistency.

Go 1.21 changes this with the introduction of log/slog, bringing native structured logging to the standard library. Instead of parsing unstructured text, structured logs use key-value pairs that can be searched, filtered, and analyzed reliably and quickly. For developers debugging production systems, this is game-changing.

Getting Started: Your First slog Application

The beauty of slog is how simple it is to begin: