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go singleton with sync.Once

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sync의 Once 를 활용하여 go 싱글톤을 구현합니다.
https://golang.org/pkg/sync/#Once

code

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package unit

import "sync"

// package level variable
var instance *Component
var once sync.Once

type Component struct {
    count int
}

func GetInstance() *Component {
    once.Do(func() {
        instance = &Component{count: 0}
    })
    return instance
}

func (s *Component) add() {
    s.count++
}

func (s *Component) getCount() int {
    return s.count
}

test code

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package test

import (
    "fmt"
    "testing"
)

func TestGetInstance(t *testing.T) {
    GetInstance().add()
    fmt.Println(GetInstance().getCount())

    GetInstance().add()
    fmt.Println(GetInstance().getCount())

    GetInstance().add()
    fmt.Println(GetInstance().getCount())
}

실행 결과

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D:\repository\singleton_test\test>go test
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PASS
ok      _/D_/repository/singleton_test/test     0.171s