Golang: fatal error: concurrent map writes

concurrentmapwrites.go

// provoke a crash by cuncurrently writing to the same map from different goroutines

package main

import (
        "fmt"
        "math/rand"
        "sync"
)

func manipulate(wait *sync.WaitGroup, m map[int]int) {
        defer wait.Done()
        for i := 0; i < 10000; i++ {
                key := rand.Intn(100)
                value := rand.Intn(99999)
                m[key] = value
        }
}

func main() {
        var wait sync.WaitGroup
        m := make(map[int]int)

        for i := 0; i < 5; i++ {
                wait.Add(1)
                go manipulate(&wait, m)
        }
        wait.Wait()
        fmt.Printf("%#v\n", m)
}