Simple http2 NodeJS Server from official docs & postman not working - node.js

Question

I am learning how to build an http2 server with NodeJS 10 LTS official documentation. I copy pasted the server side code into server.js and run node on it, but when I try to connect with postman (REST testing tool) I receive an error.
const http2 = require('http2');
const fs = require('fs');
const server = http2.createSecureServer({
key: fs.readFileSync('localhost-privkey.pem'),
cert: fs.readFileSync('localhost-cert.pem')
});
server.on('error', (err) => console.error(err));
server.on('stream', (stream, headers) => {
// stream is a Duplex
stream.respond({
'content-type': 'text/html',
':status': 200
});
stream.end('<h1>Hello World</h1>');
});
server.listen(8443);
The error I receive from postman is as follows:
Unknown ALPN Protocol, expected `h2` to be available.
If this is a HTTP request: The server was not configured with the `allowHTTP1` option or a listener for the `unknownProtocol` event.
Things I have tried to solve the problem:
As required in the official documentation I have created private and public certificate (.pem).
I have included the public certificate inside postman software. So now the only error I receive is the one mentioned above (Unknown ALPN protocol).
What else is needed to make the example in the official docs work? I could not find online resources for that, and all the previous questions on stackoverflow relates to old versions of NodeJS when http2 was not still native.

Answer 1

Try to add allowHTTP1: true in Server options at it says server not configure with the allowHTTP1
const server = http2.createSecureServer({
key: fs.readFileSync('localhost-privkey.pem'),
cert: fs.readFileSync('localhost-cert.pem')
});
To
const server = http2.createSecureServer({
key: fs.readFileSync('localhost-privkey.pem'),
cert: fs.readFileSync('localhost-cert.pem'),
allowHTTP1: true
});
From github http2 documentation :
allowHTTP1 {boolean} Incoming client connections that do not support HTTP/2 will be downgraded to HTTP/1.x when set to true. See the 'unknownProtocol' event. See ALPN negotiation. Default: false.
Here i found better answer already on Stackoverflow Configure HTTP2 NodeJS Server

Answer 2

Ok, after thorough investigation I found a satisfactory answer to a great extent.
The https request should be https://localhost:8443/stream to get a response from the server with Hello World. Without the stream path there is no response.
postman gives 403 response after installing the public certificate, but insomnia doesn't give any response.
Using google chrome developer tools in the Network tab I can finally get response 200 OK from the server as shown below.