metrics: fix issues reported by staticcheck (ethereum#20365)

metrics/librato/librato.go

@@ -42,9 +42,10 @@ func Librato(r metrics.Registry, d time.Duration, e string, t string, s string,
 
 func (re *Reporter) Run() {
 	log.Printf("WARNING: This client has been DEPRECATED! It has been moved to https://github.com/mihasya/go-metrics-librato and will be removed from rcrowley/go-metrics on August 5th 2015")
-	ticker := time.Tick(re.Interval)
+	ticker := time.NewTicker(re.Interval)
+	defer ticker.Stop()
 	metricsApi := &LibratoClient{re.Email, re.Token}
-	for now := range ticker {
+	for now := range ticker.C {
 		var metrics Batch
 		var err error
 		if metrics, err = re.BuildRequest(now, re.Registry); err != nil {

metrics/registry_test.go

@@ -270,15 +270,18 @@ func TestChildPrefixedRegistryOfChildRegister(t *testing.T) {
 	if err != nil {
 		t.Fatal(err.Error())
 	}
-	r2.Register("baz", NewCounter())
+	err = r2.Register("baz", NewCounter())
+	if err != nil {
+		t.Fatal(err.Error())
+	}
 	c := NewCounter()
 	Register("bars", c)
 
 	i := 0
 	r2.Each(func(name string, m interface{}) {
 		i++
 		if name != "prefix.prefix2.baz" {
-			//t.Fatal(name)
+			t.Fatal(name)
 		}
 	})
 	if i != 1 {
@@ -293,13 +296,15 @@ func TestWalkRegistries(t *testing.T) {
 	if err != nil {
 		t.Fatal(err.Error())
 	}
-	r2.Register("baz", NewCounter())
+	err = r2.Register("baz", NewCounter())
+	if err != nil {
+		t.Fatal(err.Error())
+	}
 	c := NewCounter()
 	Register("bars", c)
 
 	_, prefix := findPrefix(r2, "")
 	if prefix != "prefix.prefix2." {
 		t.Fatal(prefix)
 	}
-
 }

metrics/timer.go

@@ -76,10 +76,7 @@ func NewTimer() Timer {
 }
 
 // NilTimer is a no-op Timer.
-type NilTimer struct {
-	h Histogram
-	m Meter
-}
+type NilTimer struct{}
 
 // Count is a no-op.
 func (NilTimer) Count() int64 { return 0 }