chore: remove refs to deprecated io/ioutil (#376)

Signed-off-by: guoguangwu <guoguangwu@magic-shield.com>

pkg/storage/file/fstore_test.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"net/mail"
 	"os"
@@ -192,7 +191,7 @@ func TestGetLatestMessage(t *testing.T) {
 
 // setupDataStore creates a new FileDataStore in a temporary directory
 func setupDataStore(cfg config.Storage, extHost *extension.Host) (*Store, *bytes.Buffer) {
-	path, err := ioutil.TempDir("", "inbucket")
+	path, err := os.MkdirTemp("", "inbucket")
 	if err != nil {
 		panic(err)
 	}
@@ -228,7 +227,7 @@ func deliverMessage(ds *Store, mbName string, subject string, date time.Time) (s
 		meta.To[0].Address, meta.From.Address, subject)
 	delivery := &message.Delivery{
 		Meta:   meta,
-		Reader: ioutil.NopCloser(strings.NewReader(testMsg)),
+		Reader: io.NopCloser(strings.NewReader(testMsg)),
 	}
 	id, err := ds.AddMessage(delivery)
 	if err != nil {

pkg/storage/mem/message.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"container/list"
 	"io"
-	"io/ioutil"
 	"net/mail"
 	"time"
 
@@ -47,7 +46,7 @@ func (m *Message) Subject() string { return m.subject }
 
 // Source returns a reader for the message source.
 func (m *Message) Source() (io.ReadCloser, error) {
-	return ioutil.NopCloser(bytes.NewReader(m.source)), nil
+	return io.NopCloser(bytes.NewReader(m.source)), nil
 }
 
 // Size returns the message size in bytes.

pkg/storage/mem/store.go

@@ -2,7 +2,7 @@ package mem
 
 import (
 	"fmt"
-	"io/ioutil"
+	"io"
 	"sort"
 	"strconv"
 	"sync"
@@ -62,7 +62,7 @@ func (s *Store) AddMessage(message storage.Message) (id string, err error) {
 		err = ierr
 		return
 	}
-	source, ierr := ioutil.ReadAll(r)
+	source, ierr := io.ReadAll(r)
 	if ierr != nil {
 		err = ierr
 		return