Increasing value 1000 times through channels and goroutines

Question

I need to increase x 1000 times by creating 1000 goroutines which will increase the x by one through channels. How would I do this?

package main

import (
    "fmt"
)

func main() {
    var ch = make(chan int)

    //1000 goroutines sending 1 through a channel
    var x = 0
    for i := 0; i < 1000; i++ {
        go func() {
            ch <- 1
        }()
    }

    //Here i need to increase x by value read from the channel and then stop when the last value was sent
    //But this code doesn't work
    for {
        if v, ok := <-ch; ok {
            x += v
        } else {
            break
        }
    }

    fmt.Println(x)
}

I was thinking about closing the channel at the end but I don't know how to detect when the last value was sent

Answer 1

sync.WaitGroup can be used for detecting the completion of a set of goroutines. For example:

package main

import (
    "fmt"
    "sync"
)

func main() {
    var ch = make(chan int)
    wg := &sync.WaitGroup{}

    //1000 goroutines sending 1 through a channel
    var x = 0
    for i := 0; i < 1000; i++ {
        wg.Add(1)
        go func() {
            defer wg.Done()
            ch <- 1
        }()
    }

    go func() {
        wg.Wait()
        close(ch)
    }()

    //Here i need to increase x by value read from the channel and then stop when the last value was sent
    //But this code doesn't work
    for {
        if v, ok := <-ch; ok {
            x += v
        } else {
            break
        }
    }

    fmt.Println(x)
}

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