Like it says on the tin. This prints the JA3 string and the MD5ed fingerprint.
$ curl https://ja3.joeshaw.org
771,4866-4867-4865-49196-49200-159-52393-52392-52394-49195-49199-158-49188-49192-107-49187-49191-103-49162-49172-57-49161-49171-51-157-156-61-60-53-47-255,0-11-10-13172-16-22-23-49-13-43-45-51-21,29-23-30-25-24,0-1-2
f436b9416f37d134cadd04886327d3e8
fastly compute build to compile
fastly compute serve to run locally, though it doesn't have TLS so it's not very useful.
fastly compute deploy to deploy the service.
If you want to deploy this to your own service, you will need to unset service_id in fastly.toml.