code: func (a *Agent) AnswerWithError(ctx context.Context, mid uint, err error) {
  	if ctx != nil && err != nil {
  		s := opentracing.SpanFromContext(ctx)
  		if s != nil {
  			tracing.LogError(s, err.Error())
  		}
  	}
  	p, e := util.GetErrorPayload(a.serializer, err)
  	if e != nil {
  		logger.Log.Errorf("error answering the user with an error: %s", e.Error())
  		return
  	}
  	e = a.Session.ResponseMID(ctx, mid, p, true)
  	if e != nil {
  		logger.Log.Errorf("error answering the user with an error: %s", e.Error())
  	}
  }
docs: // AnswerWithError answers with an error