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//consumer

    go func() {

        // try to read from channel, block at most 5s.

        // if timeout, print time event and go on loop.

        // if read a message which is not the type we want(we want true, not false),

        // retry to read.

        timer := time.NewTimer(time.Second * 5)

        for {

            // timer may be not active, and fired

            if !timer.Stop() {

                select {

                case <-timer.C: //try to drain from the channel，尝试抽取，由于使用select，因此这里可以保证：不阻塞 + 一定抽取成功

                default:

                }

            }

            timer.Reset(time.Second * 5)  //重置定时器

            select {

            case b := <-c:

                if b == false {

                    fmt.Println(time.Now(), ":recv false. continue")

                    continue

                }

                //we want true, not false

                fmt.Println(time.Now(), ":recv true. return")

                return

            case <-timer.C:

                fmt.Println(time.Now(), ":timer expired")

                continue

            }

        }

    }()

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go func() {

        for {

            func() {

                timer := time.NewTimer(time.Second * 2)

                defer timer.Stop()

                select {

                case b := <-c:

                    if !b {

                        fmt.Println(time.Now(), "work...")

                    }

                case <-timer.C: // BBB: normal receive from channel timeout event

                    fmt.Println(time.Now(), "timeout")

                }

            }()

        }

    }()