How to Use Prometheus Client Library in Go

Use the github.com/prometheus/client_golang library to create metrics and expose them via an HTTP endpoint.

1. Install the library with go get github.com/prometheus/client_golang/prometheus.
2. Import the package and define your metrics in your main file.
3. Register your metrics with prometheus.DefaultRegisterer.
4. Serve the metrics at /metrics using http.Handle.

package main

import (
	"net/http"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
)

var (
	requestsTotal = prometheus.NewCounter(
		prometheus.CounterOpts{
			Name: "http_requests_total",
			Help: "Total number of HTTP requests.",
		},
	)
)

func init() {
	prometheus.MustRegister(requestsTotal)
}

func main() {
	http.Handle("/metrics", promhttp.Handler())
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		requestsTotal.Inc()
		w.Write([]byte("Hello World"))
	})
	http.ListenAndServe(":8080", nil)
}

The Prometheus Client Library in Go lets your program count things like button clicks or task duration. It automatically formats these numbers so monitoring tools like Prometheus can read them. Think of it as adding a dashboard to your software that shows real-time activity.