html - 代码提前结束

Question

在我的代码中，代码在执行所有任务之前执行。我必须更改我的代码什么才能在结束前完成所有任务？

package main

import (
"fmt"
"math/rand"
"time"
)

// run x tasks at random intervals
// - a task is a goroutine that runs for 2 seconds.
// - a task runs concurrently to other task
// - the interval between task is between 0 and 2 seconds

func main() {
// set x to the number of tasks
x := 4
// random numbers generation initialization
random := rand.New(rand.NewSource(1234))

for num := 0; num < x; num++ {
    // sleep for a random amount of milliseconds             before starting a new task
    duration := time.Millisecond *                 time.Duration(random.Intn(2000))
    time.Sleep(duration)

    // run a task
    go func() {
        // this is the work, expressed by sleeping for 2          seconds
        time.Sleep(2 * time.Second)
        fmt.Println("task done")
    }()
}
}

Answer 1

是的，正如@Laney 提到的，这可以使用 WaitGroup 和 channel 来完成。请引用下面的代码。

WaitGroup :

package main

import (
    "fmt"
    "math/rand"
    "sync"
    "time"
)

// run x tasks at random intervals
// - a task is a goroutine that runs for 2 seconds.
// - a task runs concurrently to other task
// - the interval between task is between 0 and 2 seconds

func main() {
    // set x to the number of tasks
    x := 4
    // random numbers generation initialization
    var wg sync.WaitGroup
    random := rand.New(rand.NewSource(1234))

    for num := 0; num < x; num++ {
        // sleep for a random amount of milliseconds             before starting a new task
        duration := time.Millisecond * time.Duration(random.Intn(2000))
        time.Sleep(duration)
        //
        wg.Add(1)
        // run a task
        go func() {
            // this is the work, expressed by sleeping for 2 seconds
            time.Sleep(2 * time.Second)
            fmt.Println("task done")
            wg.Done()
        }()
    }
    wg.Wait()
    fmt.Println("All tasks done")
}

输出:

task done
task done
task done
task done
All tasks done

Playground 上:https://play.golang.org/p/V-olyX9Qm8

使用 channel :

package main

import (
    "fmt"
    "math/rand"
    "time"
)

// run x tasks at random intervals
// - a task is a goroutine that runs for 2 seconds.
// - a task runs concurrently to other task
// - the interval between task is between 0 and 2 seconds

func main() {
    //Channel to indicate completion of a task, can be helpful in sending a result value also
    results := make(chan int)
    // set x to the number of tasks
    x := 4
    t := 0 //task tracker
    // random numbers generation initialization
    random := rand.New(rand.NewSource(1234))

    for num := 0; num < x; num++ {
        // sleep for a random amount of milliseconds             before starting a new task
        duration := time.Millisecond * time.Duration(random.Intn(2000))
        time.Sleep(duration)
        //

        // run a task
        go func() {
            // this is the work, expressed by sleeping for 2 seconds
            time.Sleep(2 * time.Second)
            fmt.Println("task done")
            results <- 1 //may be something possibly relevant to the task

        }()
    }
    //Iterate over the channel till the number of tasks
    for result := range results {
        fmt.Println("Got result", result)
        t++
        if t == x {
            close(results)
        }
    }
    fmt.Println("All tasks done")
}

输出:

task done
task done
Got result 1
Got result 1
task done
Got result 1
task done
Got result 1
All tasks done

Playground :https://play.golang.org/p/yAFdDj5nhb