Race condition demo of a map in Go. Try `go run race_map.go` many times.

race_map.go

package main

import (
	"sync"

	"github.com/k0kubun/pp"
)

func main() {
	m := map[int]string{}

	a := 97
	var wg sync.WaitGroup

	wg.Add(10)
	for i := 0; i < 10; i++ {
		go func() {
			m[i] = string(a + i)
			wg.Done()
		}()
	}

	wg.Wait()
	pp.Printf("%v\n", m)
}