func Lease(c context.Context, maxTasks int, queueName string, leaseTime int) ([]*Task, error) {
	return lease(c, maxTasks, queueName, leaseTime, false, nil)
}
func Lease(c context.Context, maxTasks int, queueName string, leaseTime int) ([]*Task, error) {
	return lease(c, maxTasks, queueName, leaseTime, false, nil)
}
// Lease leases tasks from a queue.
// leaseTime is in seconds.
// The number of tasks fetched will be at most maxTasks.