go copy on write map

main.go

package main

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

func main() {
	m := map[string]int{}
	for i := 0; i < 1000; i++ {
		m[fmt.Sprintf("key%d", i)] = i
	}
	go func() {
		for {
			m1 := make(map[string]int)
			for k, v := range m {
				m1[k] = v
			}
			m1[time.Now().String()] = 1
			m = m1
		}
	}()
	wg := sync.WaitGroup{}
	for i := 0; i < 100; i++ {
		wg.Add(1)
		go func(wg *sync.WaitGroup, id int) {
			defer wg.Done()
			s := ""
			val := 0
			index := 0
			for {
				for k, v := range m {
					s = k
					val += v
					index++
					if index%10000 == 0 {
						fmt.Println(id, len(m), index, s)
					}
				}
			}
		}(&wg, i)
	}
	wg.Wait()
}