test: use T.TempDir to create temporary test directory (#15400)

This commit replaces `ioutil.TempDir` with `t.TempDir` in tests. The
directory created by `t.TempDir` is automatically removed when the test
and all its subtests complete.

Prior to this commit, temporary directory created using `ioutil.TempDir`
needs to be removed manually by calling `os.RemoveAll`, which is omitted
in some tests. The error handling boilerplate e.g.
	defer func() {
		if err := os.RemoveAll(dir); err != nil {
			t.Fatal(err)
		}
	}
is also tedious, but `t.TempDir` handles this for us nicely.

Reference: https://pkg.go.dev/testing#T.TempDir

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

cmd/bitrot_test.go

@@ -20,17 +20,11 @@ package cmd
 import (
 	"context"
 	"io"
-	"io/ioutil"
-	"os"
 	"testing"
 )
 
 func testBitrotReaderWriterAlgo(t *testing.T, bitrotAlgo BitrotAlgorithm) {
-	tmpDir, err := ioutil.TempDir("", "")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tmpDir)
+	tmpDir := t.TempDir()
 
 	volume := "testvol"
 	filePath := "testfile"
@@ -60,7 +54,9 @@ func testBitrotReaderWriterAlgo(t *testing.T, bitrotAlgo BitrotAlgorithm) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	writer.(io.Closer).Close()
+	if bw, ok := writer.(io.Closer); ok {
+		bw.Close()
+	}
 
 	reader := newBitrotReader(disk, nil, volume, filePath, 35, bitrotAlgo, bitrotWriterSum(writer), 10)
 	b := make([]byte, 10)
@@ -76,6 +72,9 @@ func testBitrotReaderWriterAlgo(t *testing.T, bitrotAlgo BitrotAlgorithm) {
 	if _, err = reader.ReadAt(b[:5], 30); err != nil {
 		t.Fatal(err)
 	}
+	if br, ok := reader.(io.Closer); ok {
+		br.Close()
+	}
 }
 
 func TestAllBitrotAlgorithms(t *testing.T) {