remove deprecated of package io/ioutil (#3395)

recovery.go

@@ -9,7 +9,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"net"
 	"net/http"
@@ -121,7 +120,7 @@ func stack(skip int) []byte {
 		// Print this much at least.  If we can't find the source, it won't show.
 		fmt.Fprintf(buf, "%s:%d (0x%x)\n", file, line, pc)
 		if file != lastFile {
-			data, err := ioutil.ReadFile(file)
+			data, err := os.ReadFile(file)
 			if err != nil {
 				continue
 			}