Go error handling patterns that scale: wrapping, unwrapping, sentinels

Error handling in Go is explicit by design. Every function that can fail returns an error as its last value, and callers must deal with it. That explicitness is valuable — but as your codebase grows, return err stops being enough. You lose context, callers can't distinguish failure modes, and debugging production incidents becomes guesswork. This article covers three patterns that hold up at scale: error wrapping, sentinel errors, and custom error types. Why return err Isn't Enough C