[FEATURE] For all jobs, add a global event listening function

[iakirago]

For all jobs, add a global event listening function.

When any one or more of the following events occur in any job, the set callback function will be triggered.

'EVENT_SCHEDULER_STARTED', 'EVENT_SCHEDULER_SHUTDOWN', 'EVENT_SCHEDULER_PAUSED', 'EVENT_SCHEDULER_RESUMED', 'EVENT_ALL_JOBS_REMOVED','EVENT_JOB_ADDED', 'EVENT_JOB_REMOVED', 'EVENT_JOB_MODIFIED', 'EVENT_JOB_EXECUTED', 'EVENT_JOB_ERROR', 'EVENT_JOB_MISSED'

Hope to have the following implementation，

package main

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

func myListenerFunc() {
	fmt.Println("myListenerFunc")
}

func main() {
	s := gocron.NewScheduler(time.UTC)

	s.Every("1s").Do(func() {})
	s.Every("1s").Do(func() {})
	s.Every("1s").Do(func() {})
	s.Every("1s").Do(func() {})
	s.Every("1s").Do(func() {})

	s.SetEventListener(myListenerFunc, EVENT_JOB_EXECUTED|EVENT_JOB_ERROR)
	s.StartBlocking()
}

The above is my suggestion, and the idea also has shortcomings, such as how myListenerFunc distinguishes different events and performs different logic functions. Please correct any deficiencies. Due to limited personal ability, I can only propose this idea, thank you!

[JohnRoesler]

At least some initial events exist and can be set globally now.

Feel free to open additional feature requests as you use it