golang-design-patterns

Golang Design Patterns & Refactoring

Expert-level code refactoring and design pattern application for Go. Detects code smells, suggests refactoring strategies, and applies proven design patterns to improve maintainability.

When to Apply

Use this skill when:

• Refactoring complex or legacy code
• Reducing technical debt
• Extracting reusable patterns
• Simplifying large functions (God Objects)
• Improving code maintainability
• Applying Gang of Four patterns to Go

Rule Categories by Priority

Priority	Count	Focus
High	2	Critical refactoring needs
Medium	11	Code quality improvements

Rules Covered (13 total)

High-Impact Patterns (2)

• high-god-object - Extract logic from 300+ line functions
• high-extract-method - Name complex code blocks with descriptive methods

Medium Improvements (11)

• medium-primitive-obsession - Replace primitives with value objects
• medium-long-parameter-list - Use parameter objects for >5 params
• medium-data-clumps - Extract repeated parameter groups
• medium-feature-envy - Move logic closer to data
• medium-magic-constants - Replace magic numbers with named constants
• medium-builder-pattern - Fluent API for complex construction
• medium-factory-constructor - Validated object creation
• medium-introduce-parameter-object - Group related parameters
• medium-switch-to-strategy - Replace type switches with interfaces
• medium-middleware-decorator - Decorator pattern for http.Handler
• medium-law-of-demeter - Reduce coupling, avoid message chains

Common Refactoring Patterns

God Object → Extracted Methods

// ❌ 500 line function
func (u *Usecase) Process() { ... }

// ✅ Extracted methods
func (u *Usecase) Process() {
    u.validate()
    u.transform()
    u.persist()
}

Primitive Obsession → Value Object

// ❌ Primitive types
func CreateUser(email string) { ... }

// ✅ Value object
type Email struct { value string }
func CreateUser(email Email) { ... }