code: func (mc *metricContext) Observe(err error) error {
  	apiMetrics.latency.WithLabelValues(mc.attributes...).Observe(
  		time.Since(mc.start).Seconds())
  	if err != nil {
  		apiMetrics.errors.WithLabelValues(mc.attributes...).Inc()
  	}
  
  	return err
  }
docs: // Observe the result of a API call.