chore: for backward compatibility (#4852)

Signed-off-by: kevin <wanjunfeng@gmail.com>

core/syncx/once.go

@@ -0,0 +1,9 @@
+package syncx
+
+import "sync"
+
+// Once returns a func that guarantees fn can only called once.
+// Deprecated: use sync.OnceFunc instead.
+func Once(fn func()) func() {
+	return sync.OnceFunc(fn)
+}

core/syncx/once_test.go

@@ -0,0 +1,33 @@
+package syncx
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestOnce(t *testing.T) {
+	var v int
+	add := Once(func() {
+		v++
+	})
+
+	for i := 0; i < 5; i++ {
+		add()
+	}
+
+	assert.Equal(t, 1, v)
+}
+
+func BenchmarkOnce(b *testing.B) {
+	var v int
+	add := Once(func() {
+		v++
+	})
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		add()
+	}
+	assert.Equal(b, 1, v)
+}