為什么 goroutine 不會阻塞 time.Sleep(duration)

Question

我運行的程序：

package main

import (
    "flag"
    "fmt"
    "os"
    "os/signal"
    "time"
)

var sleepSeconds string
var timeToSleep time.Duration

func init() {
    flag.StringVar(&sleepSeconds, "sleep", "1s", "-sleep \"3s\"")
}

func main() {
    startTime := time.Now()
    fmt.Println("Start Time: ", startTime)
    c := make(chan os.Signal)
    signal.Notify(c, os.Interrupt)

    // Block until a signal is received.
    flag.Parse()
    timeToSleep, err := time.ParseDuration(sleepSeconds)
    if err != nil {
        fmt.Println("unable to parse the duration: ", err)
        return
    }
    fmt.Println("Time to Sleep: ", timeToSleep)

    myChan := make(chan string)
    go one(myChan)
    go two(myChan)
    go three(myChan)
    var s os.Signal
    fmt.Println("Signal is, ", s)
    go func() {
        s = <-c
        fmt.Println("After receiving Signal is, ", s)

    }()
    i := 0
    for {
        i++
        generatedString := fmt.Sprintf("%d", i)
        fmt.Println("Generating... ", generatedString)
        myChan <- generatedString
        //      time.Sleep(timeToSleep)
        fmt.Println("Length of Channel: ", len(myChan))
        if s != nil {
            break
        }
    }
    fmt.Println("Total time the program ran for: ", time.Since(startTime))
}

func one(dataCh chan string) {
    for val := range dataCh {
        fmt.Printf("Value received in func one: %s\n", val)
        time.Sleep(timeToSleep)
    }
}

func two(dataCh chan string) {
    for val := range dataCh {
        fmt.Printf("Value received in func two: %s\n", val)
        time.Sleep(timeToSleep)
    }
}

func three(dataCh chan string) {
    for val := range dataCh {
        fmt.Printf("Value received in func three: %s\n", val)
        time.Sleep(timeToSleep)
    }
}

當我使用以下標志（5s）運行此程序時

./ichan -sleep "5s" > data.txt

輸出令人費解，因為我看到程序只運行了2.31606525s但所有 3 個 goroutine 都應該被阻塞至少 5 秒。 data.txt 是此存儲庫的一部分以供參考，代碼也可在同一存儲庫中找到。

我的問題是：函數one 、 two和three中的 time.Sleep() 應該被阻塞，直到睡眠持續時間，然后從通道中消耗字符串，但觀察到睡眠對 goroutines 沒有任何影響.

Answer 1

timeToSleep, err :=創建一個名為 timeToSleep 的新局部變量，該變量獨立於同名的包級別變量，因此包級別變量始終為零。

您似乎錯過了本機持續時間標志類型： https : //pkg.go.dev/flag#DurationVar

func init() {
    flag.DurationVar(&timeToSleep, "sleep", 1*time.Second, `-sleep "3s"`)
}

Answer 2

同一程序的工作副本

package main

import (
    "flag"
    "fmt"
    "os"
    "os/signal"
    "time"
)

var sleepSeconds string
var timeToSleep time.Duration
var err error

func init() {
    flag.StringVar(&sleepSeconds, "sleep", "1s", "-sleep \"3s\"")
}

func main() {
    startTime := time.Now()
    fmt.Println("Start Time: ", startTime)
    c := make(chan os.Signal)
    signal.Notify(c, os.Interrupt)

    // Block until a signal is received.
    flag.Parse()
    timeToSleep, err = time.ParseDuration(sleepSeconds)
    if err != nil {
        fmt.Println("unable to parse the duration: ", err)
        return
    }
    fmt.Println("Time to Sleep: ", timeToSleep)

    myChan := make(chan string)
    go one(myChan)
    go two(myChan)
    go three(myChan)
    var s os.Signal
    fmt.Println("Signal is, ", s)
    go func() {
        s = <-c
        fmt.Println("After receiving Signal is, ", s)

    }()
    i := 0
    for {
        i++
        generatedString := fmt.Sprintf("%d", i)
        fmt.Println("Generating... ", generatedString)
        myChan <- generatedString
        //      time.Sleep(timeToSleep)
        fmt.Println("Length of Channel: ", len(myChan))
        if s != nil {
            break
        }
    }
    fmt.Println("Total time the program ran for: ", time.Since(startTime))
}

func one(dataCh chan string) {
    for val := range dataCh {
        fmt.Printf("Value received in func one: %s\n", val)
        time.Sleep(timeToSleep)
    }
}

func two(dataCh chan string) {
    for val := range dataCh {
        fmt.Printf("Value received in func two: %s\n", val)
        time.Sleep(timeToSleep)
    }
}

func three(dataCh chan string) {
    for val := range dataCh {
        fmt.Printf("Value received in func three: %s\n", val)
        time.Sleep(timeToSleep)
    }
}