Creational Patterns in Go

Factory, Builder, Singleton

Core
2026-04-17T12:05:42+00:00
Go implements Factory, Builder, and Singleton patterns manually using functions, structs, and sync.Once instead of built-in language features.

Go does not have built-in Factory, Builder, or Singleton patterns; you implement them manually using functions, structs, and pointers. Use a constructor function for a Factory, a method-chaining struct for a Builder, and a package-level variable with a sync.Once guard for a Singleton.

// Singleton example
var instance *MyType
var once sync.Once

func GetInstance() *MyType {
	once.Do(func() {
		instance = &MyType{}
	})
	return instance
}

// Factory example
func NewMyType(config Config) *MyType {
	return &MyType{config: config}
}

// Builder example
type MyTypeBuilder struct {
	config Config
}

func (b *MyTypeBuilder) SetOpt(opt string) *MyTypeBuilder {
	b.config.Opt = opt
	return b
}

func (b *MyTypeBuilder) Build() *MyType {
	return &MyType{config: b.config}
}