Cancellation support

[Brcrwilliams]

Right now, this library does not seem to have built-in support for cancellation. I feel like this is something that is probably needed by ~90% of use-cases, even if it's for something as simple as being able to quit the program on SIGTERM. I've been able to work around this by creating a wrapper around the library like this:

package scheduler

import (
	"context"

	"github.com/robfig/cron"
)

type Job interface {
	// Run executes the cron task. It should cancel whatever it
	// is doing upon receiving a signal from ctx.Done.
	Run(context.Context)
}

// CronScheduler can run tasks on a cron schedule, with cancellation.
type CronScheduler struct {
	runner *cron.Cron
}

func NewCronScheduler() *CronScheduler {
	return &CronScheduler{runner: cron.New()}
}

func (s *CronScheduler) Run(ctx context.Context) {
	go func() { s.runner.Run() }()
	for range ctx.Done() {
		s.runner.Stop()
		return
	}
}

// bit of a hack so that we can pass a context into cron.Schedule
type jobWrapper struct {
	ctx     context.Context
	runFunc func(context.Context)
}

func (j *jobWrapper) Run() {
	j.runFunc(j.ctx)
}

func (s *CronScheduler) Schedule(ctx context.Context, schedule cron.Schedule, job Job) {
	wrapper := &jobWrapper{
		ctx:     ctx,
		runFunc: job.Run,
	}

	s.runner.Schedule(schedule, wrapper)
}

It would be really great if the interfaces provided by this library accepted contexts to support cancellation, deadlines, etc.

[defool]

Hope for the built-in support.

[defool]

There is Remove function to cancel job: https://github.com/robfig/cron/blob/master/cron.go#L204