package main

import (
	"context"
	"fmt"
	"time"
)

func worker(ctx context.Context, jobs <-chan int, out chan<- int) {
	for {
		select {
		case <-ctx.Done():
			return
		case n, ok := <-jobs:
			if !ok {
				return
			}
			out <- n * n
		}
	}
}
func main() {
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()
	jobs := make(chan int)
	out := make(chan int)
	go worker(ctx, jobs, out)
	go func() {
		defer close(jobs)
		for _, n := range []int{2, 3, 4} {
			jobs <- n
		}
	}()
	for i := 0; i < 3; i++ {
		fmt.Println(<-out)
	}
}