code: func New(bk backend.Backend) (Service, error) {
  	s := &server{
  		bk:    bk,
  		clock: clockwork.NewRealClock(),
  	}
  	if s.activeSessionTTL == 0 {
  		s.activeSessionTTL = defaults.ActiveSessionTTL
  	}
  	return s, nil
  }
docs: // New returns new session server that uses sqlite to manage
  // active sessions