Russian language synthesizer web speech api?

Question

speech synthesis

Can you tell me how the Russian language is synthesized through the web speech api or how does google do it in the browser?
doesn't work like that

var app = new SpeechSynthesisUtterance('Привет мир!');
app.lang = 'ru';
window.speechSynthesis.speak(app);

works great in english

var app = new SpeechSynthesisUtterance('Hello world!');
window.speechSynthesis.speak(app);

Answer 1

var speech = new SpeechSynthesisUtterance();
    speech.lang = 'ru-RU';
    speech.rate = 1.5;
    speech.pitch = 2;
    speech.volume = 1;
    speech.txt = "Привет, как дела?";
    window.speechSynthesis.speak(speech);