If it was my case, I still undecided which reverse proxy can replace Nginx, however, there are no known performance benchmarks for Caddy 2 I could refer to.
Nginx was designed to handle backend services easily and programmers from different background may not be well verse in Golang at the beginning.
It is generally repeated that the Go stdlib webserver is internet-facing-ok and production-ready (with appropriate timeouts being set on the http.Server), making a reverse proxy unnecessary.
There are also dead-simple TLS libraries, some that will even get LE certs automatically.
Agreed, I have recently built a web server entirely (with timeouts) in Go too and acme.sh for LE certs but I still haven't find a way to support Wordpress from Go to PHP-FPM, I'm not well verse to fix the only this part, if you have any suggestion is greatly appreciate.
Nginx was designed to handle backend services easily and programmers from different background may not be well verse in Golang at the beginning.