code: func (nc *Conn) SubscribeSync(subj string) (*Subscription, error) {
  	if nc == nil {
  		return nil, ErrInvalidConnection
  	}
  	mch := make(chan *Msg, nc.Opts.SubChanLen)
  	s, e := nc.subscribe(subj, _EMPTY_, nil, mch, true)
  	return s, e
  }
docs: // SubscribeSync will express interest on the given subject. Messages will
  // be received synchronously using Subscription.NextMsg().