Unless you have a wild use-case that hasn't been tackled by what's out there, why on earth would rolling your own be a good idea? Building a proper, secure, and performant API gateway is NOT a few dozen lines of code.
There are some super robust (and fast) Go API gateways that take care of all the things you didn't think about when trying to roll your own.
I can absolutely assure you that building a fast and secure gateway is not as hard as you seem to be implying. This is, again, based on my real world experience.
There are some super robust (and fast) Go API gateways that take care of all the things you didn't think about when trying to roll your own.