metrics: replace time.Tick with time.NewTicker to prevent resource leaks

time.Tick() creates a ticker whose underlying resources can never be
released because there is no handle to call Stop(). This is flagged
by go vet (SA1015).

6 files in metrics/ fixed: debug.go, json.go, log.go, opentsdb.go,
syslog.go, writer.go.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

metrics/debug.go

@@ -22,7 +22,9 @@ var (
 // CaptureDebugGCStats captures new values for the Go garbage collector statistics
 // exported in debug.GCStats. This is designed to be called as a goroutine.
 func CaptureDebugGCStats(r Registry, d time.Duration) {
-	for range time.Tick(d) {
+	ticker := time.NewTicker(d)
+	defer ticker.Stop()
+	for range ticker.C {
 		CaptureDebugGCStatsOnce(r)
 	}
 }

metrics/json.go

@@ -15,7 +15,9 @@ func (r *StandardRegistry) MarshalJSON() ([]byte, error) {
 // WriteJSON writes metrics from the given registry  periodically to the
 // specified io.Writer as JSON.
 func WriteJSON(r Registry, d time.Duration, w io.Writer) {
-	for range time.Tick(d) {
+	ticker := time.NewTicker(d)
+	defer ticker.Stop()
+	for range ticker.C {
 		WriteJSONOnce(r, w)
 	}
 }

metrics/log.go

@@ -18,7 +18,9 @@ func LogScaled(r Registry, freq time.Duration, scale time.Duration, l Logger) {
 	du := float64(scale)
 	duSuffix := scale.String()[1:]
 
-	for range time.Tick(freq) {
+	ticker := time.NewTicker(freq)
+	defer ticker.Stop()
+	for range ticker.C {
 		r.Each(func(name string, i interface{}) {
 			switch metric := i.(type) {
 			case *Counter:

metrics/opentsdb.go

@@ -39,7 +39,9 @@ func OpenTSDB(r Registry, d time.Duration, prefix string, addr *net.TCPAddr) {
 // OpenTSDBWithConfig is a blocking exporter function just like OpenTSDB,
 // but it takes a OpenTSDBConfig instead.
 func OpenTSDBWithConfig(c OpenTSDBConfig) {
-	for range time.Tick(c.FlushInterval) {
+	ticker := time.NewTicker(c.FlushInterval)
+	defer ticker.Stop()
+	for range ticker.C {
 		if err := openTSDB(&c); nil != err {
 			log.Println(err)
 		}

metrics/syslog.go

@@ -12,7 +12,9 @@ import (
 // Syslog outputs each metric in the given registry to syslog periodically using
 // the given syslogger.
 func Syslog(r Registry, d time.Duration, w *syslog.Writer) {
-	for range time.Tick(d) {
+	ticker := time.NewTicker(d)
+	defer ticker.Stop()
+	for range ticker.C {
 		r.Each(func(name string, i interface{}) {
 			switch metric := i.(type) {
 			case *Counter:

metrics/writer.go

@@ -11,7 +11,9 @@ import (
 // Write sorts writes each metric in the given registry periodically to the
 // given io.Writer.
 func Write(r Registry, d time.Duration, w io.Writer) {
-	for range time.Tick(d) {
+	ticker := time.NewTicker(d)
+	defer ticker.Stop()
+	for range ticker.C {
 		WriteOnce(r, w)
 	}
 }