chainntnfs: use T.TempDir to create temporary test directory

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

chainntnfs/btcdnotify/btcd_test.go

@@ -5,7 +5,6 @@ package btcdnotify
 
 import (
 	"bytes"
-	"io/ioutil"
 	"testing"
 
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
@@ -33,10 +32,12 @@ var (
 func initHintCache(t *testing.T) *chainntnfs.HeightHintCache {
 	t.Helper()
 
-	tempDir, err := ioutil.TempDir("", "kek")
-	require.NoError(t, err, "unable to create temp dir")
-	db, err := channeldb.Open(tempDir)
+	db, err := channeldb.Open(t.TempDir())
 	require.NoError(t, err, "unable to create db")
+	t.Cleanup(func() {
+		require.NoError(t, db.Close())
+	})
+
 	testCfg := chainntnfs.CacheConfig{
 		QueryDisable: false,
 	}