code: func New(cfg Config) (producers.MetricsProducer, chan producers.MetricsMessage) {
  	p := promProducer{
  		config:             cfg,
  		store:              store.New(),
  		metricsChan:        make(chan producers.MetricsMessage),
  		janitorRunInterval: 60 * time.Second,
  	}
  	return &p, p.metricsChan
  }
docs: // New returns a prometheus producer and a channel for passing in metrics