Express: SSE not working

[x7airworker]

Using the following code, the connection can be opened, but no data gets sended:

app.get('/stream', (req, res) => {
    res.setHeader('Cache-Control', 'no-cache');
    res.setHeader('Content-Type', 'text/event-stream');
    res.setHeader('Connection', 'keep-alive');
    res.flushHeaders();
    
    res.write("data: Hello World!\n\n");
})

With res.end() I am able to close to connection and send all messages at once.
This issue could also be related to #22.