Replace deprecated ioutil with io and os (#20776)

* Replace ioutil with io and os

* Replace ioutil in utils/file.go

* Minor fix to tests and excluded files

Co-authored-by: Tim Scheuermann <tim.scheuermann@mattermost.com>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

cmd/mattermost/commands/cmdtestlib.go

@@ -9,7 +9,6 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -127,7 +126,7 @@ func (h *testHelper) SetConfig(config *model.Config) {
 	if err != nil {
 		panic("failed to marshal config: " + err.Error())
 	}
-	if err := ioutil.WriteFile(h.configFilePath, buf, 0600); err != nil {
+	if err := os.WriteFile(h.configFilePath, buf, 0600); err != nil {
 		panic("failed to write file " + h.configFilePath + ": " + err.Error())
 	}
 }

cmd/mattermost/commands/server_test.go

@@ -4,7 +4,6 @@
 package commands
 
 import (
-	"io/ioutil"
 	"net"
 	"os"
 	"syscall"
@@ -77,7 +76,7 @@ func TestRunServerSystemdNotification(t *testing.T) {
 	defer th.TearDownServerTest()
 
 	// Get a random temporary filename for using as a mock systemd socket
-	socketFile, err := ioutil.TempFile("", "mattermost-systemd-mock-socket-")
+	socketFile, err := os.CreateTemp("", "mattermost-systemd-mock-socket-")
 	if err != nil {
 		panic(err)
 	}