Usage
注册任务到调度器里，当任务要执行的时候会使用goroutines调用，这样每个任务都不会发生阻塞。
Golang不仅仅是兼容了linux标准的crontab格式，而且扩展了秒。也就是说正常的crontab是 分 时 小时 月 星期，而robfig cron是 秒 分 时 日 月 星期。
c := cron.New()
c.AddFunc("0 30 * * * *", func() { fmt.Println("Every hour on the half hour") })
c.AddFunc("@hourly", func() { fmt.Println("Every hour") })
c.AddFunc("@every 1h30m", func() { fmt.Println("Every hour thirty") })
c.Start()
//这些任务都是异步执行的.
c.AddFunc("@daily", func() { fmt.Println("Every day") })
//获取他下次执行的时间.
inspect(c.Entries())
//关闭着计划任务, 但是不能关闭已经在执行中的任务.
c.Stop()
CRON Expression Format
A cron expression represents a set of times, using 6 space-separated fields.
| Field name | Mandatory? | Allowed values | Allowed special characters |
|---|---|---|---|
| Seconds | Yes | 0-59 | * / , - |
| Minutes | Yes | 0-59 | * / , - |
| Hours | Yes | 0-23 | * / , - |
| Day of month | Yes | 1-31 | * / , - ? |
| Month | Yes | 1-12 or JAN-DEC | * / , - |
| Day of week | Yes | 0-6 or SUN-SAT | * / , - ? |
Predefined schedules
You may use one of several pre-defined schedules in place of a cron expression.
| Entry | Description | Equivalent To |
|---|---|---|
| @yearly (or @annually) | Run once a year, midnight, Jan. 1st | 0 0 0 1 1 * |
| @monthly | Run once a month, midnight, first of month | 0 0 0 1 * * |
| @weekly | Run once a week, midnight on Sunday | 0 0 0 * * 0 |
| @daily (or @midnight) | Run once a day, midnight | 0 0 0 * * * |
| @hourly | Run once an hour, beginning of hour | 0 0 * * * * |
