Idiomatic semaphore example in Go (using Buffered Channels)

semaphore.go

// Idiomatic Semaphore Example in Go
// Lucas Wagner

// Golang has no built-in facility to implement semaphores, so a common design 
// pattern is to use buffered channels.

package main

import (
  "fmt"
  "time"
)

func printIt(sem chan bool, msg string, iter int){

	// release the resource when we're done
	defer func () { <-sem } ()

	fmt.Println(msg, " ", iter)

}

func main() {

	resourcePool := 3
	sem := make(chan bool, resourcePool)

	for i := 0 ; i < 10 ; i++ {
    
    // pause for the scheduler
    time.Sleep(100 * time.Millisecond)
    
		// acquire a single resource
		sem <- true

		go printIt(sem, "Test ", i)

	}

	// acquire the resources back; then we know it's done
  for j := 0 ; j < resourcePool ; j++ {
		sem <- true
	}
  
}