下面是我的代碼示例?，F(xiàn)在我想在我的代碼中添加直方圖。但是我找不到像這樣添加直方圖的方法。有人可以幫助我嗎？我能夠編寫(xiě)直方圖示例，但我無(wú)法將其添加到下面的代碼中package mainimport (    "github.com/prometheus/client_golang/prometheus"    "github.com/prometheus/client_golang/prometheus/promhttp"    "github.com/prometheus/common/log"    "net/http")type fooCollector struct {    fooMetric *prometheus.Desc}func newFooCollector(label1 string) *fooCollector {    return &fooCollector{        fooMetric: prometheus.NewDesc("fff_metric",            "Shows whether a foo has occurred in our cluster",            nil, prometheus.Labels{"env":label1},        ),            }}func (collector *fooCollector) Describe(ch chan<- *prometheus.Desc) {    //Update this section with the each metric you create for a given collector    ch <- collector.fooMetric}func (collector *fooCollector) Collect(ch chan<- prometheus.Metric) {    ch <- prometheus.MustNewConstMetric(collector.fooMetric, prometheus.GaugeValue, 111111)}func main() {    prometheus.MustRegister(newFooCollector("dev"))    http.Handle("/metrics", promhttp.Handler())    http.ListenAndServe(":80", nil)}