1. Singleton Pattern

Singleton creational design pattern restricts the instantiation of a type to a single object.

1.1. Implementation

package singleton

type singleton map[string]string

var (
    once sync.Once

    instance singleton
)

func New() singleton {
    once.Do(func() {
        instance = make(singleton)
    })

    return instance
}

1.2. Usage

s := singleton.New()

s["this"] = "that"

s2 := singleton.New()

fmt.Println("This is ", s2["this"])
// This is that

1.3. Rules of Thumb

• Singleton pattern represents a global state and most of the time reduces testability.