[FEATURE] - run a job on the last weekday of the month

[rsvix]

Describe the bug

Gocron cronjob cant parse "LW", errors with invalid syntax

To Reproduce

`
package main
import (
"log"
"github.com/go-co-op/gocron/v2"
)
func main() {
s, err := gocron.NewScheduler()
if err != nil {
log.Fatal(err)
}

_, err = s.NewJob(
	gocron.CronJob("0 0 5 LW * ?", true),
	gocron.NewTask(func() {
		log.Println("Test job 1")
	}),
)
if err != nil {
	log.Printf("Test job 1 err: %v", err)
}

_, err = s.NewJob(
	gocron.CronJob("0 5 LW * ?", false),
	gocron.NewTask(func() {
		log.Println("Test job 2")
	}),
)
if err != nil {
	log.Printf("Test job 2 err: %v", err)
}

s.Start()
for {
}

}
`

Version

v2.13.0

Expected behavior

The expression should be parsed since its a valid cron expression

[JohnRoesler]

Hi @rsvix,

A few thoughts:

• L W ? are all consider non-standard, and aren't including in all Cron implementations. https://en.wikipedia.org/wiki/Cron#Non-standard_characters
• gocron uses https://github.com/robfig/cron for parsing cron syntax, and it's not supported over there, although there are some issues / PRs related
  • is there a way to support set a spec as last day of the month like 0 0 8 L * ? robfig/cron#299
  • Run Cron last Monday of month robfig/cron#319
  • add L support with no changes on the SpecSchedule structure or whatsoever robfig/cron#325

Is it fair to say, this is actually a feature request to support:

• The ability to run a job on the last weekday of the month?

[rsvix]

Hello @JohnRoesler,

Thats fair, i will update it to a feature request
Sad that https://github.com/robfig/cron seems to be abandoned and the PRs are still not merged.