.Do overrides existing cron tasks

[Tigraine]

I ran into a really nasty issue with StartImmediately and .Do().
Basically the following code will behave completely un-expected:

func main() {
	scheduler := gocron.NewScheduler(time.UTC)
	scheduler.Every(15 * time.Second).Do(func() {
		log.Printf("normal cron at: %v", time.Now())
	})
	scheduler.StartAsync()

	timer := time.NewTimer(5 * time.Second)
	<-timer.C
	scheduler.StartImmediately().Do(func() {
		log.Printf("Something completely different")
	})

	blockUntilTermSignal()
}

The output is:

2021/11/29 13:34:10 normal cron at: 2021-11-29 13:34:10.541174 +0100 CET m=+0.001237376
2021/11/29 13:34:25 Something completely different
2021/11/29 13:34:30 Something completely different

So until the subsequent/unqualified .Do() call the scheduler will run the "normal" 15 second func, but once a .Do is set it replaces the existing one with the newly passed func.

The (for me) expected output should have been:

2021/11/29 13:35:10 normal cron at: 2021-11-29 13:35:10.215062 +0100 CET m=+0.000477251
2021/11/29 13:35:15 Something completely different
2021/11/29 13:35:25 normal cron at: 2021-11-29 13:35:25.220175 +0100 CET m=+15.005519585

To get to this I had to change the code to:

        scheduler.Every(1).Millisecond().LimitRunsTo(1).Do(func() {
		log.Printf("Something completely different")
	})

I can understand that this is probably a mistake on my part or that I am mis-using the libs fluent interface - but then again this code looks totally normal and when reading this I'd expect to be scheduling 2 separate jobs - not to replace the existing payload :/

Maybe some safeguards can be inserted into Do to prevent it from overriding the previous already submitted func?

[JohnRoesler]

Hey @Tigraine this repo is no longer maintained. We're keeping an active fork over at https://github.com/go-co-op/gocron

Feel free to open an issue over there!

I'll post something here quickly: what I am seeing is that we aren't handling this properly, but the first method that needs to be called is Every() or Cron() which instantiates the job. So in this case, StartImmediately() is being called it's grabbing the current job which is your "normal cron" job and then changing the frequency at which it runs.