Use os.ReadFile().

fcm.go

@@ -15,11 +15,12 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
+	"os"
 	"sync"
 
 	"git.bit5.ru/backend/errors"
+
 	"github.com/go-logr/logr"
 	"golang.org/x/oauth2"
 
@@ -64,7 +65,7 @@ type Credentials struct {
 }
 
 func ReadCredentialsFromFile(filename string) (Credentials, error) {
-	data, err := ioutil.ReadFile(filename)
+	data, err := os.ReadFile(filename)
 	if err != nil {
 		return Credentials{}, errors.WithStack(err)
 	}