The biggest webservices of today like google search, facebook, aws are all written using models that your parent suggests. Are you saying if these guys rewrite all their code in Go, they will basically cut down 50% of their operation costs or something? What exactly does 'worker can do something else' translate to?

Technically, yes - the workers can be multithreaded. If you put multithreaded workers behind an event-loop web server (both nginx or apache can do this), then they can handle many http keep-alives as well. It's not the same thing as using an event loop throughout the whole stack, but it's pretty effective.

When you take the time to learn relational databases, sql, normalization and maybe some caching, suddenly you don't find yourself spending very much time waiting on the DB.

If something indeed is going to take that long, perhaps you shouldn't be making the user wait on it either. Queue that shit.