Golang Error Handling Standards

Priority: P0 (CRITICAL)

Principles

• Errors are Values: Handle them like any other value.
• Handle Once: Log OR Return. Never Log AND Return (creates duplicate logs).
• Add Context: Don't just return err bubble up. Wrap it with context: fmt.Errorf("failed to open file: %w", err).
• Use Standard Lib: Go 1.13+ errors package (Is, As, Unwrap) is sufficient. Avoid pkg/errors (deprecated).

Guidelines

• Sentinel Errors: Expoted, fixed errors (io.EOF, sql.ErrNoRows). Use errors.Is(err, io.EOF).
• Error Types: Structs implementing error. Use errors.As(err, &target).
• Panic: Only for unrecoverable startup errors.

Anti-Patterns

• Check only not nil: if err != nil { return err } -> Loses stack/context context.
• String checking: err.Error() == "foo" -> Brittle.
• Swallowing errors: _ = func() -> Dangerous.

References

• Error Wrapping Patterns