How to Accurately Count and Manage Active Goroutines in Go?

How to Count and Display the Number of Active Goroutines

In this code, we have a queue and a function deen that performs both dequeueing and enqueueing:

var element int

func deen(queue chan int) {
    element := <-queue
    fmt.Println("element is ", element)
    if element%2 == 0 {
        fmt.Println("new element is ", element)
        queue <- (element*100 + 11)
        queue <- (element*100 + 33)
    }
}

func main() {
    queue := make(chan int, 10)
    queue <- 1
    queue <- 2
    queue <- 3
    queue <- 0
    for len(queue) != 0 {
        for i := 0; i < 2; i++ {
            go deen(queue)
        }
    }
    fmt.Scanln()
    fmt.Println("list is has len", len(queue)) //this must be 0
}

However, there is no way to print the current number of active goroutines.

Using runtime.NumGoroutine

While there is a way to get the total number of active goroutines using runtime.NumGoroutine, it's not the best approach. This is because the loops will continue spawning goroutines, leading to unnecessary CPU consumption.

A Better Approach: Using a Sync.WaitGroup

A more efficient approach is to use a sync.WaitGroup, which lets us keep track of the number of active goroutines.

func deen(wg *sync.WaitGroup, queue chan int) {
    for element := range queue {
        fmt.Println("element is ", element)
        if element%2 == 0 {
            fmt.Println("new element is ", element)
            wg.Add(2)
            queue <- (element*100 + 11)
            queue <- (element*100 + 33)
        }
        wg.Done()
    }
}

func main() {
    var wg sync.WaitGroup
    queue := make(chan int, 10)
    queue <- 1
    queue <- 2
    queue <- 3
    queue <- 0
    for i := 0; i < 4; i++ {
        wg.Add(1)
        go deen(&amp;wg, queue)
    }
    wg.Wait()
    close(queue)
    fmt.Println("list len", len(queue)) //this must be 0
}

Here, we start with four goroutines and wait until they finish their work before closing the queue. This approach provides a cleaner and more controlled way to manage the number of active goroutines.

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