feat: slow threshold customizable in redis (#1185)

* feat: slow threshold customizable in redis

* chore: improve config robustness

core/conf/time_test.go

@@ -0,0 +1,14 @@
+package conf
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCheckedDuration(t *testing.T) {
+	assert.Equal(t, time.Second, CheckedDuration(1000))
+	assert.Equal(t, 2*time.Second, CheckedDuration(2000))
+	assert.Equal(t, 2*time.Second, CheckedDuration(time.Second*2))
+}