Go- 函数执行时间

package main
import (	"fmt"	"time")
func main() {	start := time.Now()	fmt.Printf("Now time is %d\n", start)
	func() {		for a, i := 0, 0; i < 1e10 && a < 1e10; i++ {			a = i		}	}()
	end := time.Now()	cost := end.Sub(start)	fmt.Printf("Cost time is %d\n", cost) // 单位为纳秒}