const http2 = require('http2');
const server = http2.createSecureServer({cert, key}, onRequest);
 
function push (stream, filePath) {  
    const {file, headers} = getFile(filePath);
    const pushHeaders = {[HTTP2_HEADER_PATH]: filePath };
 
    stream.pushStream(pushHeaders, (pushStream) => {
        pushStream.respondWithFD(file, headers);
    });
}
 
function onRequest (req, res) {  
    // Push files with index.html
    if (reqPath === '/index.html') {
        push(res.stream, 'bundle1.js');
        push(res.stream, 'bundle2.js');
    }
 
    // Serve file
    res.stream.respondWithFD(file.fileDescriptor, file.headers);
}

Source : HTTP/2 Server Push with Node.js

Pour HTTP/2 avec Express, on peut utiliser spdy.