Concurrent example

concurrent.go

package main

import (
	"errors"
	"fmt"
	"runtime"
	"sync"
)

// Concurrent is concurrently execute tasks for number of CPUs.
func Concurrent(items chan any, task func(any)) {
	WithN(runtime.NumCPU(), items, task)
}

// WithN is concurrently execute tasks for number of threads.
func WithN(threads int, items chan any, task func(any)) {
	if len(items) < 1 {
		return
	}

	if len(items) < threads || threads < 0 {
		threads = len(items)
	}

	var wg sync.WaitGroup
	wg.Add(len(items))
	for i := 0; i < threads; i++ {
		execute(&wg, items, task)
	}
	wg.Wait()
}

// Execute is execute task in goroutine.
func execute(wg *sync.WaitGroup, items chan any, task func(any)) {
	go func() {
		for value := range items {
			task(value)
			wg.Done()
		}
	}()
}

func main() {
	values := []string{"Honoka", "Kotori", "Umi", "Maki", "Rin", "Hanayo", "Nico", "Nozomi", "Eli"}
	items := make(chan any, len(values))
	defer close(items)
	for _, value := range values {
		items <- value
	}

	rejects := make(chan error, len(values))
	defer close(rejects)
	Concurrent(items, func(value any) {
		if value == "Honoka" || value == "Kotori" || value == "Hanayo" {
			rejects <- errors.New("fight dayo!")
			return
		}
		fmt.Println(value)
	})
	for {
		select {
		case err := <-rejects:
			fmt.Println(err)
		default:
			return
		}
	}
}