channelrace.go

package main

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

func main() {
    fmt.Println("ready? start!")
    runtime.GOMAXPROCS(4)

    var state   = 0
    var send    = make(chan int)
    var receive = make(chan int)
    var racers  = 10
    var laps    = 10
    var wg sync.WaitGroup

    fmt.Println("lauching race")
    //manager
    go func() {
        send <- state
        for {
          select {
            case current := <-receive:
              state = current
            case <-time.After(5 * time.Millisecond):
              send <- state
          }
        }
    }()

    wg.Add(racers)
    for w := 0; w < racers; w++ {
        go func() {
            defer wg.Done()
            for x := 0; x < laps; x++ {
                current := <-send
                current = current + 1
                fmt.Println(current)
                time.Sleep(10 * time.Millisecond)
                receive <- current
                time.Sleep(4 * time.Millisecond)
            }
        }()
        fmt.Println("launched ", w)
    }

    wg.Wait()
    fmt.Println("state:", state)
}