counting-sema.go

// example of counting semaphore to control fixed no. of goroutines
package main

import (
	"fmt"
	"time"
)

func main() {

	// fixed no. of goroutines that are allowed to run at a time
	sema := make(chan struct{}, 5)

	for i := 0; i < 100; i++ {
		sema <- struct{}{}
		go func(i int) {
			fmt.Println(i)
			time.Sleep(1 * time.Second)
			<-sema
		}(i)
	}
}