Every returns a crontab Schedule that activates once every duration.

New returns an error if cannot create new worker.

Parse returns a new crontab schedule representing the given spec.

Start all workers.

Stop all workers.

Wait blocks until all workers will be stopped.

ErrAlreadyWorker is returned by New calls when workers name is already exists.

ErrWrongOptions is returned by New calls when parameter Options.Schedule is NIL or Options.Handler is NIL.