3.10 计算代码运行的时长

package main

import (
	"fmt"
	"sync"
	"time"
)

func main() {

	t := time.NewTimer(3 * time.Second)
	fmt.Printf("Start waiting at %v\n", time.Now().Format(time.UnixDate))
	<-t.C
	fmt.Printf("Code executed at %v\n", time.Now().Format(time.UnixDate))

	wg := &sync.WaitGroup{}
	wg.Add(1)
	fmt.Printf("Start waiting for AfterFunc at %v\n", time.Now().Format(time.UnixDate))
	time.AfterFunc(3*time.Second, func() {
		fmt.Printf("Code executed for AfterFunc at %v\n", time.Now().Format(time.UnixDate))
		wg.Done()
	})

	wg.Wait()

	fmt.Printf("Waiting on time.After at %v\n", time.Now().Format(time.UnixDate))
	<-time.After(3 * time.Second)
	fmt.Printf("Code resumed at %v\n", time.Now().Format(time.UnixDate))

}

/*

Start waiting at Thu Mar 22 00:32:42 CST 2018
Code executed at Thu Mar 22 00:32:45 CST 2018
Start waiting for AfterFunc at Thu Mar 22 00:32:45 CST 2018
Code executed for AfterFunc at Thu Mar 22 00:32:48 CST 2018
Waiting on time.After at Thu Mar 22 00:32:48 CST 2018
Code resumed at Thu Mar 22 00:32:51 CST 2018

*/