Support HTTP/2 over cleartext (H2C) with prior knowledge

[salim-b]

Describe the feature request

It would be nice if Gatus could accept HTTP/2 over cleartext TCP (H2C) with prior knowledge, so that if Gatus is used behind a proxy that terminates TLS (like the one from fly.io), the request isn't downgraded to HTTP/1.1 before being forwarded to Gatus. This would yield better performance / consume less resources.

H2C support for Golang is offered in golang.org/x/net/http2/h2c, a full example is found here.

Thanks for taking this into consideration!

Why do you personally want this feature to be implemented?

Better performance when hosting Gatus on fly.io.

How long have you been using this project?

~1.5 years

Additional information

• Fly.io documentation of the relevant services.ports.http_options.h2_backend config option.