use Duration for doorOpenTime + lint

godoor_server/godoor_server.go

@@ -217,7 +217,7 @@ func (doobserver *DoorBoyServer) postKeepDoorOpen(w http.ResponseWriter, r *http
 	rs, _ := io.ReadAll(r.Body)
 	parsedTime, err := time.Parse(time.RFC3339, strings.TrimSpace(string(rs)))
 	if err != nil {
-		fmt.Println("Error with parsing time: %v", err)
+		fmt.Printf("Error with parsing time: %v", err)
 		w.WriteHeader(http.StatusBadRequest)
 	}
 	keepOpenUntil = &parsedTime
@@ -229,6 +229,9 @@ func main() {
 
 	var dumpKeys []cardToken
 	savedKeys, err := os.ReadFile("keys.json")
+	if err != nil {
+		log.Fatalf("reading saved keys from keys.json: %v", err)
+	}
 
 	err = json.Unmarshal(savedKeys, &dumpKeys)
 	if err == nil {
@@ -268,7 +271,7 @@ func main() {
 	keyLock.Lock()
 	data, err := json.Marshal(keys)
 	if err == nil {
-		os.WriteFile("keys.json", data, 0600)
+		os.WriteFile("keys.json", data, 0o600)
 		log.Println("Saved keys successfully!")
 	}
 	keyLock.Unlock()