refactor: move from io/ioutil to io and os package (#1772)

The io/ioutil package has been deprecated as of Go 1.16, see
https://golang.org/doc/go1.16#ioutil. This commit replaces the existing
io/ioutil functions with their new definitions in io and os packages.

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

pkg/utils/file_test.go

@@ -1,7 +1,6 @@
 package utils
 
 import (
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"testing"
@@ -53,11 +52,11 @@ func TestDirExists(t *testing.T) {
 	const st = "stash_tmp"
 
 	tmp := os.TempDir()
-	tmpDir, err := ioutil.TempDir(tmp, st) // create a tmp dir in the system's tmp folder
+	tmpDir, err := os.MkdirTemp(tmp, st) // create a tmp dir in the system's tmp folder
 	if err == nil {
 		defer os.RemoveAll(tmpDir)
 
-		tmpFile, err := ioutil.TempFile(tmpDir, st)
+		tmpFile, err := os.CreateTemp(tmpDir, st)
 		if err != nil {
 			return
 		}