diff --git a/collector.go b/collector.go
index a67986f..c16d121 100644
--- a/collector.go
+++ b/collector.go
@@ -23,7 +23,7 @@ func (c *client) RegisterCollector(rc RegisterCollectorFunc) {
 	})
 }
 
-var colOnceMap sync.Map
+var colOnce sync.Once
 var col = &collector{
 	delayLengthDesc: prometheus.NewDesc(
 		prometheus.BuildFQName(namespace, "delay", "queue_length"),
@@ -40,8 +40,7 @@ type collector struct {
 
 func registerCollector(rc RegisterCollectorFunc, c *client) {
 	col.cs.Store(c, struct{}{})
-	m, _ := colOnceMap.LoadOrStore(rc, &sync.Once{})
-	m.(*sync.Once).Do(func() {
+	colOnce.Do(func() {
 		rc(col)
 	})
 }
diff --git a/metric.go b/metric.go
index ce0ddc6..906a94d 100644
--- a/metric.go
+++ b/metric.go
@@ -17,7 +17,7 @@ const (
 )
 
 var (
-	metricOnceMap                                                          sync.Map
+	metricOnce                                                             sync.Once
 	metric                                                                 *prometheus.SummaryVec
 	errMetric, hitsMetric, missMetric                                      *prometheus.CounterVec
 	delayPollErrorMetric, delayReclaimErrorMetric, delayReclaimCountMetric *prometheus.CounterVec
@@ -55,8 +55,7 @@ func init() {
 }
 
 func registerMetric(rc RegisterCollectorFunc) {
-	m, _ := metricOnceMap.LoadOrStore(rc, &sync.Once{})
-	m.(*sync.Once).Do(func() {
+	metricOnce.Do(func() {
 		rc(errMetric)
 		rc(hitsMetric)
 		rc(missMetric)