A really bad data race

race.go

package main

import (
        "flag"
        "runtime"
)

var (
        n     = flag.Int("n", 8, "Number of counting functions")
        count = flag.Int("max", 1e5, "Number to count down from")
)

func main() {
        flag.Parse()

        // One for collector and scheduler
        runtime.GOMAXPROCS(*n + 2)

        done := make(chan bool, *n)

        counter := *count
        for i := 0; i < *n; i++ {
                go func(mod, id int) {
                        for counter > 0 {
                                if counter%mod == id {
                                        counter--
                                }
                        }
                        done <- true
                }(*n, i)
        }

        for i := 0; i < *n; i++ {
                <-done
        }
}