test(registry): Add goleak-based goroutine leak detection

Signed-off-by: hyunuk <nnhope@hotmail.com>

Author: surinkim

go.mod

@@ -23,6 +23,7 @@ require (
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/mwitkow/go-conntrack v0.0.0-20190716064945-2f068394615f // indirect
+	go.uber.org/goleak v1.2.0 // indirect
 	golang.org/x/net v0.35.0 // indirect
 	golang.org/x/oauth2 v0.25.0 // indirect
 	golang.org/x/text v0.22.0 // indirect

go.sum

@@ -46,6 +46,8 @@ github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
 github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+go.uber.org/goleak v1.2.0 h1:xqgm/S+aQvhWFTtR0XK3Jvg7z8kGV8P4X14IzwN3Eqk=
+go.uber.org/goleak v1.2.0/go.mod h1:XJYK+MuIchqpmGmUSAzotztawfKvYLUIgg7guXrwVUo=
 golang.org/x/net v0.35.0 h1:T5GQRQb2y08kTAByq9L4/bz8cipCdA8FbRTXewonqY8=
 golang.org/x/net v0.35.0/go.mod h1:EglIi67kWsHKlRzzVMUD93VMSWGFOMSZgxFjparz1Qk=
 golang.org/x/oauth2 v0.25.0 h1:CY4y7XT9v0cRI9oupztF8AgiIu99L/ksR/Xp/6jrZ70=

prometheus/registry_test.go

@@ -39,6 +39,7 @@ import (
 	"github.com/prometheus/common/expfmt"
 	"google.golang.org/protobuf/proto"
 	"google.golang.org/protobuf/types/known/timestamppb"
+	"go.uber.org/goleak"
 )
 
 // uncheckedCollector wraps a Collector but its Describe method yields no Desc.
@@ -1339,3 +1340,28 @@ func TestCheckMetricConsistency(t *testing.T) {
 	}
 	reg.Unregister(invalidCollector)
 }
+
+func TestGatherDoesNotLeakGoroutines(t *testing.T) {
+	// Use goleak to verify that no unexpected goroutines are leaked during the test.
+	defer goleak.VerifyNone(t)
+
+	// Create a new Prometheus registry without any default collectors.
+	reg := prometheus.NewRegistry()
+
+	// Register 100 simple Gauge metrics with distinct names and constant labels.
+	for i := 0; i < 100; i++ {
+		reg.MustRegister(prometheus.NewGauge(prometheus.GaugeOpts{
+			Name:        "test_metric_" + string(rune(i)),
+			Help:        "Test metric",
+			ConstLabels: prometheus.Labels{"id": string(rune(i))},
+		}))
+	}
+
+	// Call Gather repeatedly to simulate stress and check for potential goroutine leaks.
+	for i := 0; i < 1000; i++ {
+		_, err := reg.Gather()
+		if err != nil {
+			t.Fatalf("unexpected error from Gather: %v", err)
+		}
+	}
+}