Control the number of simultaneous executions of the printNumber function without modifying it

It is necessary to implement a limiter that prevents the printNumber function from executing more than five times simultaneously, without modifying the function itself.

package main

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

func main() {
    wgGroup := sync.WaitGroup{}
    sem := make(chan struct{}, 5)

    for idx := 0; idx < 10; idx++ {
        wgGroup.Add(1)
        go func(num int) {
            defer wgGroup.Done()
            printNumber(sem, num)
        }(idx)
    }

    wgGroup.Wait()
    close(sem)
}

func printNumber(ch chan struct{}, n int) {
    ch <- struct{}{}
    time.Sleep(time.Second)
    fmt.Println(n)
    <-ch
}