计划任务框架 -- cron

项目地址：
https://github.com/robfig/cron

用法：

 package main
 import (
     "fmt"
     "github.com/robfig/cron/v3"
 )
 func main() {
     ch := make(chan int)
     c := cron.New(cron.WithSeconds())
     c.AddFunc("* * * * * *", func() {
         fmt.Println("one")
     })
     c.AddFunc("* * * * * *", func() {
         fmt.Println("two")
     })
     c.AddFunc("* * * * * *", func() {
         fmt.Println("three")
     })
     c.Start()
     <- ch
 }