2022-05-19

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package main

import (
    "context"
    "fmt"
    "sync"
    "time"

    "golang.org/x/time/rate"
)

var printMux sync.Mutex

func print(i int, status string) {
    printMux.Lock()
    defer printMux.Unlock()
    fmt.Printf("%s %3d %s \n", time.Now(), i, status)
}

var mux sync.Mutex
var limiter *rate.Limiter

func checkAndRun(j int, wg *sync.WaitGroup) {
    defer wg.Done()
    if !mux.TryLock() {
        print(j, "return")
        return
    }
    print(j, "locked at")
    _ = limiter.Wait(context.Background())

    print(j, "after wait")
    mux.Unlock()
    print(j, "end+++++++++++++++++++++++++")
}
func main() {
    runTimes := 50
    limiter = rate.NewLimiter(1, 1)

    print(-1, "start")
    var wg sync.WaitGroup
    wg.Add(runTimes)
    for i := 0; i < runTimes; i++ {
        time.Sleep(100 * time.Millisecond)
        go checkAndRun(i, &wg)
    }
    wg.Wait()
    print(-1, "END")
}