Add support for prometheus

stats/server.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"net/http"
 
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"go.uber.org/zap"
 
 	"github.com/9seconds/mtg/config"
@@ -32,6 +33,7 @@ func startServer(conf *config.Config) {
 			log.Errorw("Cannot encode json", "error", err)
 		}
 	})
+	http.Handle("/prometheus/", promhttp.Handler())
 
 	if err := http.ListenAndServe(conf.StatAddr(), nil); err != nil {
 		log.Fatalw("Stats server has been stopped", "error", err)