You're missing the sysadmin angle of this entirely. Nginx has amazing tooling around load balancing, configuration mgmt, multiple languages, logging options, rewrite rules, rate limiting, file upload size tuning, HTTP tuning in general, the list goes on and on. What if your site needs to support multiple backends like a JVM app, a wsgi app, and an old crufty cgi app. You gonna write backends for all that shit too in Go?

Sorry but I'm not going to be writing ansible code that modifies structs inside of some program then compiles said program. No thank you that sounds like crazy town. Also other sysadmins and infrastructure engineers will actually know how things work and won't have to go reading the source code for some crazy Go app program at 2am that also is a webserver for some reason?

Separation of concerns, use it!!