Error Compile in ESP8266

[febritecno]

E:\USER\Documents\Arduino\libraries\onesignal\src\OneSignal.cpp: In member function 'const char* OneSignal::sendNotificationToAudience(OSNotification&, OSAudience&)':

E:\USER\Documents\Arduino\libraries\onesignal\src\OneSignal.cpp:53:109: error: 'syncMakePOSTRequest' was not declared in this scope

 const char *result = syncMakePOSTRequest(ONESIGNAL_POST_NOTIFICATION_URL, builder.stringValue(), _apiKey);

                                                                                                         ^

[febritecno]

solved by ammarfaizi2 => check mirror repo https://github.com/ammarfaizi2/OneSignal-ESP8266