add DoWithJobDetails passes a copy of the job to the jobFunc

[JohnRoesler]

What does this do?

• adds a new method DoWithJobDetails that expects the passed jobFunc to have the it's final function parameter be a gocron.Job
  • an error is returned if the function doesn't meet this requirement
• changes the Job mutex to be inside a pointer struct inside the Job to allow copying the job struct not by pointer
• copy's the job parameters slice, since slices are by reference, to avoid a race condition with the executor calling the params
• move the schedule next run logic before running the job so the job knows it's next run during the current run

Which issue(s) does this PR fix/relate to?

resolves #299

closes #251

List any changes that modify/break current functionality

Have you included tests for your changes?

👍

Did you document any new/modified functionality?

• Updated example_test.go
• Updated README.md

Notes

main test code

package main

import (
	"github.com/go-co-op/gocron"
	"log"
	"time"
)

func task(job gocron.Job) {
	log.Printf("job last run: %s, this run: %s, job next run: %s", job.LastRun(), time.Now(), job.NextRun())
}

func main() {
	s := gocron.NewScheduler(time.Local)
	_, err := s.Tag("tag1").Every("1s").DoWithJobDetails(task)
	if err != nil {
		log.Fatalf("something went wrong: %v", err)
	}
	s.StartBlocking()
}

Output

2022/03/05 23:41:27 job last run: 0001-01-01 00:00:00 +0000 UTC,        this run: 2022-03-05 23:41:27.058901 -0600 CST m=+0.000511084, job next run: 2022-03-05 23:41:28.058794 -0600 CST
2022/03/05 23:41:28 job last run: 2022-03-05 23:41:27.058795 -0600 CST, this run: 2022-03-05 23:41:28.059964 -0600 CST m=+1.001576834, job next run: 2022-03-05 23:41:29.059843 -0600 CST
2022/03/05 23:41:29 job last run: 2022-03-05 23:41:28.059869 -0600 CST, this run: 2022-03-05 23:41:29.061094 -0600 CST m=+2.002707918, job next run: 2022-03-05 23:41:30.060961 -0600 CST
2022/03/05 23:41:30 job last run: 2022-03-05 23:41:29.061044 -0600 CST, this run: 2022-03-05 23:41:30.062407 -0600 CST m=+3.004022834, job next run: 2022-03-05 23:41:31.062168 -0600 CST
2022/03/05 23:41:31 job last run: 2022-03-05 23:41:30.062301 -0600 CST, this run: 2022-03-05 23:41:31.063563 -0600 CST m=+4.005180626, job next run: 2022-03-05 23:41:32.06342 -0600 CST

[JohnRoesler]

This is missing a big piece right now. The next run isn't calculated until after the job is run. That's a key piece of information the caller might like to know. That will require some additional digging into.

Updated

[defc0n]

Thanks for this!

[JohnRoesler]

let me know how it works for you!

[defc0n]

let me know how it works for you!

Believe it is working for me and fixes my race condition when determining the next time the job will run, thanks. Took me a bit of time to realize the task function is passed as the first argument to DoWithJobDetails() but received as the last argument in that task function.