service

cronkit

note: https://godoc.org/github.com/robfig/cron

c := cron.New()
// New中选择可以配置秒
c.AddFunc("30 * * * *", func() { fmt.Println("Every hour on the half hour") })
c.AddFunc("30 3-6,20-23 * * *", func() { fmt.Println(".. in the range 3-6am, 8-11pm") })
c.AddFunc("CRON_TZ=Asia/Tokyo 30 04 * * *", func() { fmt.Println("Runs at 04:30 Tokyo time every day") })
c.AddFunc("@hourly",      func() { fmt.Println("Every hour, starting an hour from now") })
c.AddFunc("@every 1h30m10s", func() { fmt.Println("Every hour thirty, starting an hour thirty from now") })
c.Start()
..
// Funcs are invoked in their own goroutine, asynchronously.
...
// Funcs may also be added to a running Cron
c.AddFunc("@daily", func() { fmt.Println("Every day") })
..
// Inspect the cron job entries' next and previous run times.
inspect(c.Entries())
..
c.Stop()  // Stop the scheduler (does not stop any jobs already running).

cron库语法说明：

cron format: 
Field name   | Mandatory? | Allowed values  | Allowed special characters
----------   | ---------- | --------------  | --------------------------
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  | * / , - ?

job wrappers: 
- Recover any panics from jobs (activated by default)
- Delay a job's execution if the previous run hasn't completed yet
- Skip a job's execution if the previous run hasn't completed yet
- Log each job's invocations