code: func (c *Consumer) ContainerEnvelopes(appGuid, authToken string) ([]*events.Envelope, error) {
  	envelopes, err := c.readTC(appGuid, authToken, "containermetrics")
  	if err != nil {
  		return nil, err
  	}
  	for _, env := range envelopes {
  		if env.GetEventType() == events.Envelope_LogMessage {
  			return nil, errors.New(fmt.Sprintf("Upstream error: %s", env.GetLogMessage().GetMessage()))
  		}
  	}
  	return envelopes, nil
  }
docs: // ContainerEnvelopes connects to trafficcontroller via its 'containermetrics'
  // http(s) endpoint and returns the most recent dropsonde envelopes for an app.