refactor: move from io/ioutil to io and os package

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>

mount/mount_linux_test.go

@@ -18,7 +18,6 @@ package mount
 
 import (
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -105,7 +104,7 @@ func TestFUSEHelper(t *testing.T) {
 	if err != nil {
 		t.Skip("fuse-overlayfs not installed")
 	}
-	td, err := ioutil.TempDir("", "fuse")
+	td, err := os.MkdirTemp("", "fuse")
 	if err != nil {
 		t.Fatal(err)
 	}