Go Best Practices

Go Best Practices

Follows type-first, functional, and error handling patterns from CLAUDE.md. This skill covers language-specific idioms only.

Make Illegal States Unrepresentable

Use Go's type system to prevent invalid states at compile time.

Custom types for domain primitives:

// Distinct types prevent mixing up IDs
type UserID string
type OrderID string

func GetUser(id UserID) (*User, error) {
    // Compiler prevents passing OrderID here
}

// Methods attach behavior to the type
func (id UserID) String() string {
    return string(id)
}

Interfaces for behavior contracts:

// Define what you need, not what you have
type UserRepository interface {
    GetByID(ctx context.Context, id UserID) (*User, error)
    Save(ctx context.Context, user *User) error
}

// Accept interfaces, return structs
func ProcessInput(r io.Reader) ([]byte, error) {
    return io.ReadAll(r)
}

Enums with iota and exhaustive switch:

type Status int

const (
    StatusActive Status = iota + 1
    StatusInactive
    StatusPending
)