How to use sync.WaitGroup to execute all goroutines?

php editor Apple introduces you a practical method to execute all goroutines - sync.WaitGroup. In the Go language, goroutine is a lightweight thread that can perform multiple tasks at the same time. However, sometimes we need to wait for all goroutines to complete before proceeding to the next step. At this time, sync.WaitGroup comes in handy. It provides a simple and effective way to wait for all goroutines to complete, ensuring the correct execution order of the program. Next, we will introduce in detail how to use sync.WaitGroup to implement this function.

Question content

Currently I am pushing all values ​​to a channel and reading from them and calculating their square. I want to avoid using time.sleep(2000 * time.millisecond) as it will block execution for 2 seconds, instead I want each goroutine to be processed and wait for its execution, then exit the program. I just moved away from golang, so now asking this basic question :(. Can anyone help me solve this problem?

package main

import (
    "fmt"
    "sync"
    "time"
)

func doSquare(num int) int {
    return num * num
}

var wg sync.WaitGroup

func main() {

    wg.Add(1)
    st := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
    quit := make(chan bool)
    ch := make(chan int)
    go func() {
        for i := range st {
            ch <- i
        }
    }()

    go func() {
        for {
            select {
            case x := <-ch:
                fmt.Println(doSquare(x))
                // return

            case <-quit:
                wg.Done()
            default:
                // fmt.Println("---")
                // do something
            }
        }
    }()

    quit <- true

    wg.Wait()
    time.Sleep(2000 * time.Millisecond)
}

Solution

Just move qui​​t <- true to the end of the first goroutine

func main() {
    wg.add(1)
    st := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
    quit := make(chan bool)
    ch := make(chan int)
    go func() {
        for i := range st {
            ch <- i
        }
        quit <- true
    }()

    go func() {
        for {
            select {
            case x := <-ch:
                fmt.println(dosquare(x))
                // return

            case <-quit:
                wg.done()
                return
            default:
                // fmt.println("---")
                // do something
            }
        }
    }()

    wg.wait()
}

This is close(ch) Another way of saying there is no more data

func main() {
    st := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
    quit := make(chan bool)
    ch := make(chan int) // improve concurrency by `ch := make(chan int, 100)`
    go func() {
        for i := range st {
            ch <- i
        }
        close(ch)
    }()

    go func() {
        for x := range ch {
            fmt.Println(doSquare(x))
        }
        quit <- true
    }()

    <-quit
}

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