refactor: move from io/ioutil to io and os package (#2592)

cmd/frpc/sub/reload.go

@@ -17,7 +17,7 @@ package sub
 import (
 	"encoding/base64"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"os"
 	"strings"
@@ -76,7 +76,7 @@ func reload(clientCfg config.ClientCommonConf) error {
 		return nil
 	}
 
-	body, err := ioutil.ReadAll(resp.Body)
+	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return err
 	}