I just published webmention-run, a Google Run application written in Go that implements Webmention. I’m now using this to handle webmentions on bitworking.org. Given the generous free quota for Google Run I don’t expect this to cost me anything. This is on top of using Firebase Hosting to host the static (Jekyll) parts of my blog, which is also effectively free.
Another awesome feature is that both services will provide SSL certificates; in
my case Firebase Hosting provides the cert for https://bitworking.org, and
Google Cloud Run provides the SSL cert for the subdomain where my instance of
webmention-run is running, which is the subdomain