type CounterOption … type counterOptions … func (co counterOptions) apply(o prom.CounterOpts) prom.CounterOpts { … } // WithConstLabels allows you to add ConstLabels to Counter metrics. func WithConstLabels(labels prom.Labels) CounterOption { … } type HistogramOption … // WithHistogramBuckets allows you to specify custom bucket ranges for histograms if EnableHandlingTimeHistogram is on. func WithHistogramBuckets(buckets []float64) HistogramOption { … } // WithHistogramConstLabels allows you to add custom ConstLabels to // histograms metrics. func WithHistogramConstLabels(labels prom.Labels) HistogramOption { … }