concurrently.go

package concurrently

import (
	"sync"
	"sync/atomic"
)

type Task interface {
	Do()
}

type TaskFunc func()

func (t TaskFunc) Do() {
	t()
}

func Concurrently(concurrency int, tasks []Task) {
	tasksLen := int32(len(tasks))

	var taskIdx int32 = -1

	var wg sync.WaitGroup

	wg.Add(len(tasks))

	for i := 0; i < concurrency; i++ {
		go func() {
			for {
				// this approach is 3x faster than using channels
				i := atomic.AddInt32(&taskIdx, 1)

				if i >= tasksLen {
					return
				}

				tasks[i].Do()
				wg.Done()
			}
		}()
	}

	wg.Wait()
}