為什么goroutine不會阻塞time.Sleep(duration)

我運行的程式：

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）運行此程式時

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

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

我的問題是：在功能time.Sleep（） one，two并three都應該被阻止，直到睡眠的持續時間，然后使用來自信道的串，但觀察結果是睡眠不具有對夠程任何影響。

uj5u.com熱心網友回復：

timeToSleep, err := 創建一個名為 timeToSleep 的新區域變數，該變數獨立于同名的包級別變數，因此包級別變數始終為零。

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

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

uj5u.com熱心網友回復：

同一程式的作業副本

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)
    }
}

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