go

# Go Patterns Reference for Go-specific patterns, idioms, and best practices. Full bibliography: `references/sources.md`. ## Iron Law > **ERRORS ARE VALUES** [5][7] > > Never ignore errors. `if err != nil` is correctness, not boilerplate. Every error > return must be checked, wrapped with context, or explicitly documented as intentionally > ignored with `_ = fn()`. "Errors are values. Values can be programmed." — Rob Pike [5] ## When This Skill Activates Working with Go codebases — error handling, interfaces, goroutines, channels, packages. --- ## Error Handling [5][6] ```go // BAD: return err — caller loses context // GOOD: return fmt.Errorf("reading config %s: %w", path, err) var ErrNotFound = errors.New("not found") func FindUser(id string) (*User, error) { u, err := db.Get(id) if err != nil { return nil, fmt.Errorf("finding user %s: %w", id, err) } if u == nil { return nil, ErrNotFound } return u, nil } // Caller: if errors.Is(err, ErrNotFound) { ... } ``` --- ## Interface Design [7][14] ```go // "The bigger the interface, the weaker the abstraction" — Rob Pike [7] // BAD: func NewService(repo *PostgresRepo) *Service // GOOD: func NewService(repo Repository) *Service — accept interfaces [14] // Small interfaces compose cleanly [1] type Reader interface { Read(p []byte) (n int, err error) } type Writer interface { Write(p []byte) (n int, err error) } type ReadWriter interface { Reader; Writer } ``` --- ## Concurrency [9][10][13]...