go - 如何获得时间。滴答立即滴答

Question

我有一个迭代循环，直到作业启动并运行:

ticker := time.NewTicker(time.Second * 2)
defer ticker.Stop()

started := time.Now()
for now := range ticker.C {
    job, err := client.Job(jobID)
    switch err.(type) {
    case DoesNotExistError:
        continue
    case InternalError:
        return err
    }

    if job.State == "running" {
        break
    }

    if now.Sub(started) > time.Minute*2 {
        return fmt.Errorf("timed out waiting for job")
    }
}

在生产中效果很好。唯一的问题是它使我的测试变慢。他们都至少等待 2 秒才能完成。有没有办法让 time.Tick 立即打勾？

Answer 1

不幸的是，它seems Go 开发人员在任何可预见的 future 都不会添加此类功能，因此我们必须应对...

有两种常用的代码使用方式:

for 循环

给定这样的东西:

ticker := time.NewTicker(period)
defer ticker.Stop()
for <- ticker.C {
    ...
}

使用:

ticker := time.NewTicker(period)
defer ticker.Stop()
for ; true; <- ticker.C {
    ...
}

for-select循环

给定这样的东西:

interrupt := make(chan os.Signal, 1)
signal.Notify(interrupt, os.Interrupt)

ticker := time.NewTicker(period)
defer ticker.Stop()

loop:
for {
    select {
        case <- ticker.C: 
            f()
        case <- interrupt:
            break loop
    }
}

使用:

interrupt := make(chan os.Signal, 1)
signal.Notify(interrupt, os.Interrupt)

ticker := time.NewTicker(period)
defer ticker.Stop()

loop:
for {
    f()

    select {
        case <- ticker.C: 
            continue
        case <- interrupt:
            break loop
    }
}

为什么不直接使用 time.Tick()？

While Tick is useful for clients that have no need to shut down the Ticker, be aware that without a way to shut it down the underlying Ticker cannot be recovered by the garbage collector; it "leaks".

https://golang.org/pkg/time/#Tick