client_go_counter_example.go

package main

import (
	"log"
	"net/http"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
)

var (
	requests = prometheus.NewCounter(
		prometheus.CounterOpts{
			Name: "requests_total",
			Help: "Number of requests.",
		},
	)
)

func init() {
	// Metrics have to be registered to be exposed:
	prometheus.MustRegister(requests)
}

func main() {
        http.HandleFunc("/",
		func(w http.ResponseWriter, r *http.Request) {
                    requests.Inc()
        })
	// The Handler function provides a default handler to expose metrics
	// via an HTTP server. "/metrics" is the usual endpoint for that.
	http.Handle("/metrics", promhttp.Handler())
	log.Fatal(http.ListenAndServe(":8080", nil))
}