Replace deprecated ioutil

As of Go 1.16, the same functionality is now provided by package io or
package os, and those implementations should be preferred in new code.

backend/googlecloudstorage/googlecloudstorage.go

@@ -19,8 +19,8 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
+	"os"
 	"path"
 	"strconv"
 	"strings"
@@ -487,7 +487,7 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 
 	// try loading service account credentials from env variable, then from a file
 	if opt.ServiceAccountCredentials == "" && opt.ServiceAccountFile != "" {
-		loadedCreds, err := ioutil.ReadFile(env.ShellExpand(opt.ServiceAccountFile))
+		loadedCreds, err := os.ReadFile(env.ShellExpand(opt.ServiceAccountFile))
 		if err != nil {
 			return nil, fmt.Errorf("error opening service account credentials file: %w", err)
 		}