concurrency.go

package main

import (
	"log"
	"runtime"
	"sync"
	"time"
)

func main() {
	var wg sync.WaitGroup
	for i := 0; i < runtime.NumCPU(); i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			log.Printf("[computation #%d] start", i)
			compute()
			log.Printf("[computation #%d] done", i)
		}(i)
	}
	req := make(chan int)
	go func() {
		for i := range req {
			log.Printf("[server] got %d", i)
			time.Sleep(time.Second)
		}
	}()
	for i := 0; i < runtime.NumCPU(); i++ {
		req <- i
	}
	close(req)
	wg.Wait()
}

func compute() {
	fib(44)
}

func fib(n int) int {
	if n < 2 {
		return n
	}
	return fib(n-1) + fib(n-2)
}