golang timer使用

package main

import (
	"time"
	"fmt"
)

func main() {
    //創建3s的 timer
	timer := time.NewTimer(3 * time.Second)
	earliest := time.Now()
	go func() {
        //2s超時後打印時間
		select {
		case <-timer.C:
			fmt.Println("時間 ", time.Since(earliest))
			fmt.Println("Timer has expired.")
		}
	}()
    //重置爲2s
	timer.Reset(2 * time.Second)
	time.Sleep(3 * time.Second)
    //since是 現在的時間到earliest的差值
	fmt.Println("時間 ", time.Since(earliest))
}