Singleton Pattern - Golang (Simple)

main.go

package main

import (
	"fmt"
	"patterns/singleton"
)

func main() {
	singleton.Set("blabla", "aaaaa")
	fmt.Println(singleton.Get("blabla"))
}

Singleton.go

package singleton

import (
	"fmt"
	"sync"
)

//singleton variables
type singleton map[string]interface{}

var (
	// ensures that our type only gets initialized exactly once.
	once sync.Once

	instance singleton
)

//init once
func init() {
	once.Do(func() {
		fmt.Println("callll")
		instance = make(singleton)
	})
}

//Set key-value
func Set(key string, value interface{}) {
	instance[key] = value
}

//Get return value
func Get(key string) interface{} {
	return instance[key]
}

If you need design patterns there is quite a nice book

https://github.com/KeKe-Li/book/blob/master/Go/go-design-patterns.pdf