You also need to pass a `experimentalDenoServe: true` option in the options bag passed to `start()` in your `main.ts` file.
I forgot to add this to the post initially. Have retroactively added it now :)
Are there any benchmarks with the new server yet? Would be keen to see how it compares to the existing server as benchmarking on my machine showed a significant improvement over the existing http server in stdlib.