Switch from deprecated ioutil to io/os

Signed-off-by: LogicalShark <maralder@google.com>

Author: LogicalShark

cmd/auth-provider-gcp/app/getcredentials.go

@@ -19,7 +19,7 @@ package app
 import (
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"os"
 
@@ -112,7 +112,7 @@ func getCredentials(authFlow string) error {
 	if err != nil {
 		return err
 	}
-	unparsedRequest, err := ioutil.ReadAll(os.Stdin)
+	unparsedRequest, err := io.ReadAll(os.Stdin)
 	if err != nil {
 		return err
 	}

cmd/gke-gcloud-auth-plugin/cred.go

@@ -11,7 +11,7 @@ import (
 	"encoding/json"
 	"flag"
 	"fmt"
-	"io/ioutil"
+	"os"
 	"os/exec"
 	"path/filepath"
 	"strings"
@@ -369,7 +369,7 @@ func executeCommand(name string, arg ...string) ([]byte, error) {
 }
 
 func readFile(filename string) ([]byte, error) {
-	return ioutil.ReadFile(filename)
+	return os.ReadFile(filename)
 }
 
 func timeNow() time.Time {