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>

runtime/v1/linux/bundle.go

@@ -23,7 +23,6 @@ import (
 	"context"
 	"crypto/sha256"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 
@@ -70,7 +69,7 @@ func newBundle(id, path, workDir string, spec []byte) (b *bundle, err error) {
 	if err := os.MkdirAll(rootfs, 0711); err != nil {
 		return nil, err
 	}
-	err = ioutil.WriteFile(filepath.Join(path, configFilename), spec, 0666)
+	err = os.WriteFile(filepath.Join(path, configFilename), spec, 0666)
 	return &bundle{
 		id:      id,
 		path:    path,
@@ -148,7 +147,7 @@ func (b *bundle) shimAddress(namespace, socketPath string) string {
 
 func (b *bundle) loadAddress() (string, error) {
 	addressPath := filepath.Join(b.path, "address")
-	data, err := ioutil.ReadFile(addressPath)
+	data, err := os.ReadFile(addressPath)
 	if err != nil {
 		return "", err
 	}

runtime/v1/linux/runtime.go

@@ -23,7 +23,6 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"time"
@@ -288,7 +287,7 @@ func (r *Runtime) Tasks(ctx context.Context, all bool) ([]runtime.Task, error) {
 }
 
 func (r *Runtime) restoreTasks(ctx context.Context) ([]*Task, error) {
-	dir, err := ioutil.ReadDir(r.state)
+	dir, err := os.ReadDir(r.state)
 	if err != nil {
 		return nil, err
 	}
@@ -340,7 +339,7 @@ func (r *Runtime) Delete(ctx context.Context, id string) (*runtime.Exit, error)
 }
 
 func (r *Runtime) loadTasks(ctx context.Context, ns string) ([]*Task, error) {
-	dir, err := ioutil.ReadDir(filepath.Join(r.state, ns))
+	dir, err := os.ReadDir(filepath.Join(r.state, ns))
 	if err != nil {
 		return nil, err
 	}
@@ -413,7 +412,7 @@ func (r *Runtime) loadTasks(ctx context.Context, ns string) ([]*Task, error) {
 		if r.config.ShimDebug {
 			go copyAndClose(os.Stdout, shimStdoutLog)
 		} else {
-			go copyAndClose(ioutil.Discard, shimStdoutLog)
+			go copyAndClose(io.Discard, shimStdoutLog)
 		}
 
 		shimStderrLog, err := v1.OpenShimStderrLog(ctx, logDirPath)
@@ -428,7 +427,7 @@ func (r *Runtime) loadTasks(ctx context.Context, ns string) ([]*Task, error) {
 		if r.config.ShimDebug {
 			go copyAndClose(os.Stderr, shimStderrLog)
 		} else {
-			go copyAndClose(ioutil.Discard, shimStderrLog)
+			go copyAndClose(io.Discard, shimStderrLog)
 		}
 
 		t, err := newTask(id, ns, pid, s, r.events, r.tasks, bundle)

runtime/v1/shim/client/client.go

@@ -23,7 +23,6 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net"
 	"os"
 	"path/filepath"
@@ -75,8 +74,8 @@ func WithStart(binary, address, daemonAddress, cgroup string, debug bool, exitHa
 		}
 		defer f.Close()
 
-		stdoutCopy := ioutil.Discard
-		stderrCopy := ioutil.Discard
+		stdoutCopy := io.Discard
+		stderrCopy := io.Discard
 		stdoutLog, err := v1.OpenShimStdoutLog(ctx, config.WorkDir)
 		if err != nil {
 			return nil, nil, errors.Wrapf(err, "failed to create stdout log")

runtime/v1/shim/service.go

@@ -23,7 +23,6 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"sync"
@@ -543,7 +542,7 @@ func (s *Service) checkProcesses(e runc.Exit) {
 
 func shouldKillAllOnExit(ctx context.Context, bundlePath string) bool {
 	var bundleSpec specs.Spec
-	bundleConfigContents, err := ioutil.ReadFile(filepath.Join(bundlePath, "config.json"))
+	bundleConfigContents, err := os.ReadFile(filepath.Join(bundlePath, "config.json"))
 	if err != nil {
 		log.G(ctx).WithError(err).Error("shouldKillAllOnExit: failed to read config.json")
 		return true