Singleton Example for Go

singleton_main.go

package main

import (
	"fmt"
	"sync"
	"time"
)

func main() {
	go setter()

	s := Singleton()

	for i := 0; i < 30; i++ {
		v := s.Get()
		fmt.Printf("%d: %d\n", i, v)
		time.Sleep(time.Duration(1) * time.Second)
	}
}

func setter() {
	s := Singleton()

	for i := 0; i < 10; i++ {
		s.Set(i)
		time.Sleep(time.Duration(2) * time.Second)
	}
}

type singleton struct {
	i  int
	mu sync.RWMutex
}

var (
	globalS *singleton
	once    sync.Once
)

func (s *singleton) Get() int {
	s.mu.RLock()
	defer s.mu.RUnlock()

	return s.i
}

func (s *singleton) Set(v int) {
	s.mu.Lock()
	defer s.mu.Unlock()

	s.i = v
}

func Singleton() *singleton {
	once.Do(func() {
		globalS = &singleton{}
	})

	return globalS
}

On go play: https://play.golang.org/p/Yg1ee5VZTkM