code: func (s *store) ttlOpts(ctx context.Context, ttl int64) ([]clientv3.OpOption, error) {
  	if ttl == 0 {
  		return nil, nil
  	}
  	id, err := s.leaseManager.GetLease(ctx, ttl)
  	if err != nil {
  		return nil, err
  	}
  	return []clientv3.OpOption{clientv3.WithLease(id)}, nil
  }
docs: // ttlOpts returns client options based on given ttl.
  // ttl: if ttl is non-zero, it will attach the key to a lease with ttl of roughly the same length