Express Static Not Working as Expected

I have my Node.js site running static html and my server.js file is below:

const express = require('express');
const serve   = require('express-static');

const app = express();

app.use(serve('/client', {
    extensions: ['html']
}));

const server = app.listen(process.env.PORT || 3000, process.env.IP || "0.0.0.0", function(){
  console.log('server is running at %s', server.address().port);
});

I'm expecting that when I have a URL of:

http://www.example.com/my-file-name

This is pointing to this static file:

http://www.example.com/my-file-name.html

However, I am getting the following response:

Cannot GET /my-file-name

Am I misunderstanding how Express Static works? Or do I have my server.js file mis-configured?

via tonejac