feat: add counter metric

go.mod

@@ -1,3 +1,15 @@
 module metrics-counter
 
-go 1.24.1
+go 1.21.0
+
+require github.com/prometheus/client_golang v1.19.0
+
+require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.2.0 // indirect
+	github.com/prometheus/client_model v0.5.0 // indirect
+	github.com/prometheus/common v0.48.0 // indirect
+	github.com/prometheus/procfs v0.12.0 // indirect
+	golang.org/x/sys v0.16.0 // indirect
+	google.golang.org/protobuf v1.32.0 // indirect
+)

go.sum

@@ -0,0 +1,20 @@
+github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
+github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
+github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
+github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/prometheus/client_golang v1.19.0 h1:ygXvpU1AoN1MhdzckN+PyD9QJOSD4x7kmXYlnfbA6JU=
+github.com/prometheus/client_golang v1.19.0/go.mod h1:ZRM9uEAypZakd+q/x7+gmsvXdURP+DABIEIjnmDdp+k=
+github.com/prometheus/client_model v0.5.0 h1:VQw1hfvPvk3Uv6Qf29VrPF32JB6rtbgI6cYPYQjL0Qw=
+github.com/prometheus/client_model v0.5.0/go.mod h1:dTiFglRmd66nLR9Pv9f0mZi7B7fk5Pm3gvsjB5tr+kI=
+github.com/prometheus/common v0.48.0 h1:QO8U2CdOzSn1BBsmXJXduaaW+dY/5QLjfB8svtSzKKE=
+github.com/prometheus/common v0.48.0/go.mod h1:0/KsvlIEfPQCQ5I2iNSAWKPZziNCvRs5EC6ILDTlAPc=
+github.com/prometheus/procfs v0.12.0 h1:jluTpSng7V9hY0O2R9DzzJHYb2xULk9VTR1V1R/k6Bo=
+github.com/prometheus/procfs v0.12.0/go.mod h1:pcuDEFsWDnvcgNzo4EEweacyhjeA9Zk3cnaOZAZEfOo=
+golang.org/x/sys v0.16.0 h1:xWw16ngr6ZMtmxDyKyIgsE93KNKz5HKmMa3b8ALHidU=
+golang.org/x/sys v0.16.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+google.golang.org/protobuf v1.32.0 h1:pPC6BG5ex8PDFnkbrGU3EixyhKcQ2aDuBS36lqK/C7I=
+google.golang.org/protobuf v1.32.0/go.mod h1:c6P6GXX6sHbq/GpV6MGZEdwhWPcYBgnhAHhKbcUYpos=

main.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"log"
+	"net/http"
+	"os"
+	"os/signal"
+	"sync/atomic"
+	"syscall"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+var (
+	counter = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "custom_counter_total",
+			Help: "A counter that increments every 30 seconds",
+		},
+		[]string{},
+	)
+	counterValue uint64
+)
+
+func main() {
+	// Register Prometheus metrics
+	prometheus.MustRegister(counter)
+
+	// Start background counter incrementer
+	go incrementCounterEvery30s()
+
+	// Set up HTTP server
+	http.Handle("/metrics", promhttp.Handler())
+	server := &http.Server{Addr: ":8080"}
+
+	// Handle graceful shutdown
+	stop := make(chan os.Signal, 1)
+	signal.Notify(stop, os.Interrupt, syscall.SIGTERM)
+
+	go func() {
+		log.Println("Starting server on :8080")
+		if err := server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			log.Fatalf("Server error: %v", err)
+		}
+	}()
+
+	<-stop
+	log.Println("\nShutting down server...")
+}
+
+func incrementCounterEvery30s() {
+	ticker := time.NewTicker(30 * time.Second)
+	defer ticker.Stop()
+
+	for range ticker.C {
+		newVal := atomic.AddUint64(&counterValue, 1)
+		counter.WithLabelValues().Add(1)
+		log.Printf("Counter incremented to %d", newVal)
+	}
+}