main.go

package main

import (
	"io"
	"sync"
	"time"
)

// a function that does much cpu bound work
func fibo(n int) int {
	if n < 2 {
		return 1
	}
	return fibo(n-2) + fibo(n-1)
}

// run sequentially
func cpuExampleSequential() {
	for i := 0; i < 10; i++ {
		fibo(40)
	}
}

// run concurrently
func cpuExampleConcurrent() {
	var wg sync.WaitGroup

	for i := 0; i < 10; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			fibo(40)
		}()
	}

	wg.Wait()
}

type sleepReader struct {
	delay time.Duration
}

func (sr sleepReader) Read(b []byte) (int, error) {
	time.Sleep(sr.delay)
	copy(b, []byte("hello world"))
	return 0, nil
}

func read(r io.Reader) {
	b := make([]byte, 10)
	r.Read(b)
}

func ioExampleSequential() {
	for i := 0; i < 10; i++ {
		read(sleepReader{time.Second * 3})
	}
}

func ioExampleConcurrent() {
	var wg sync.WaitGroup

	for i := 0; i < 10; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			read(sleepReader{time.Second * 3})
		}()
	}

	wg.Wait()
}