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>

snapshots/testsuite/helpers.go

@@ -19,7 +19,6 @@ package testsuite
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
 	"math/rand"
 	"os"
 
@@ -30,7 +29,7 @@ import (
 )
 
 func applyToMounts(m []mount.Mount, work string, a fstest.Applier) (err error) {
-	td, err := ioutil.TempDir(work, "prepare")
+	td, err := os.MkdirTemp(work, "prepare")
 	if err != nil {
 		return errors.Wrap(err, "failed to create temp dir")
 	}
@@ -71,7 +70,7 @@ func createSnapshot(ctx context.Context, sn snapshots.Snapshotter, parent, work
 }
 
 func checkSnapshot(ctx context.Context, sn snapshots.Snapshotter, work, name, check string) (err error) {
-	td, err := ioutil.TempDir(work, "check")
+	td, err := os.MkdirTemp(work, "check")
 	if err != nil {
 		return errors.Wrap(err, "failed to create temp dir")
 	}
@@ -112,7 +111,7 @@ func checkSnapshot(ctx context.Context, sn snapshots.Snapshotter, work, name, ch
 // using the provided appliers, checking each snapshot created in a view
 // against the changes applied to a single directory.
 func checkSnapshots(ctx context.Context, sn snapshots.Snapshotter, work string, as ...fstest.Applier) error {
-	td, err := ioutil.TempDir(work, "flat")
+	td, err := os.MkdirTemp(work, "flat")
 	if err != nil {
 		return errors.Wrap(err, "failed to create temp dir")
 	}

snapshots/testsuite/testsuite.go

@@ -21,7 +21,6 @@ import (
 	//nolint:revive // go-digest needs the blank import. See https://github.com/opencontainers/go-digest#usage.
 	_ "crypto/sha256"
 	"fmt"
-	"io/ioutil"
 	"math/rand"
 	"os"
 	"path/filepath"
@@ -87,7 +86,7 @@ func makeTest(name string, snapshotterFn func(ctx context.Context, root string)
 		// 		work/ -> passed to test functions
 		// 		root/ -> passed to snapshotter
 		//
-		tmpDir, err := ioutil.TempDir("", "snapshot-suite-"+name+"-")
+		tmpDir, err := os.MkdirTemp("", "snapshot-suite-"+name+"-")
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -297,7 +296,7 @@ func checkSnapshotterStatActive(ctx context.Context, t *testing.T, snapshotter s
 	}
 	defer testutil.Unmount(t, preparing)
 
-	if err = ioutil.WriteFile(filepath.Join(preparing, "foo"), []byte("foo\n"), 0777); err != nil {
+	if err = os.WriteFile(filepath.Join(preparing, "foo"), []byte("foo\n"), 0777); err != nil {
 		t.Fatal(err)
 	}
 
@@ -331,7 +330,7 @@ func checkSnapshotterStatCommitted(ctx context.Context, t *testing.T, snapshotte
 	}
 	defer testutil.Unmount(t, preparing)
 
-	if err = ioutil.WriteFile(filepath.Join(preparing, "foo"), []byte("foo\n"), 0777); err != nil {
+	if err = os.WriteFile(filepath.Join(preparing, "foo"), []byte("foo\n"), 0777); err != nil {
 		t.Fatal(err)
 	}
 
@@ -379,7 +378,7 @@ func checkSnapshotterTransitivity(ctx context.Context, t *testing.T, snapshotter
 	}
 	defer testutil.Unmount(t, preparing)
 
-	if err = ioutil.WriteFile(filepath.Join(preparing, "foo"), []byte("foo\n"), 0777); err != nil {
+	if err = os.WriteFile(filepath.Join(preparing, "foo"), []byte("foo\n"), 0777); err != nil {
 		t.Fatal(err)
 	}
 
@@ -394,7 +393,7 @@ func checkSnapshotterTransitivity(ctx context.Context, t *testing.T, snapshotter
 	}
 	defer testutil.Unmount(t, next)
 
-	if err = ioutil.WriteFile(filepath.Join(next, "foo"), []byte("foo bar\n"), 0777); err != nil {
+	if err = os.WriteFile(filepath.Join(next, "foo"), []byte("foo bar\n"), 0777); err != nil {
 		t.Fatal(err)
 	}
 
@@ -804,7 +803,7 @@ func checkSnapshotterViewReadonly(ctx context.Context, t *testing.T, snapshotter
 	}
 
 	testfile := filepath.Join(viewMountPoint, "testfile")
-	if err := ioutil.WriteFile(testfile, []byte("testcontent"), 0777); err != nil {
+	if err := os.WriteFile(testfile, []byte("testcontent"), 0777); err != nil {
 		t.Logf("write to %q failed with %v (EROFS is expected but can be other error code)", testfile, err)
 	} else {
 		t.Fatalf("write to %q should fail (EROFS) but did not fail", testfile)