Only accept HTTP connections from Localhost in Go?

Question

I have a simple HTTP Server standing up in Golang:

h := http.NewServeMux()
h.Handle("/somepath", MyHandler)

s := &http.Server{
    Addr:    "1234",
    Handler: h,
}   

s.ListenAndServe();

What is the best way to drop connections where the caller is not localhost? Currently I'm considering inspecting the underlying connection information and ensuring that the IP Address is 127.0.0.1 , but this wastes a whole lot of resources (and runs through a whole bunch of Go code) before ultimately dropping the connection. Ideally, I can instrument the Golang server to drop the initial TCP SYN packet based on IP Address, and not create a TCP connection at all (or reveal that this port is listening).

What's the cleanest path forward here?

Answer 1

Converting VonC 's comment into an answer.

You can bind the host by setting host:port in your http.Server.Addr or http.ListenAndServe .

They use net.Listen internally.

From net.Listen :

For TCP and UDP, the syntax of laddr is "host:port", like "127.0.0.1:8080". If host is omitted, as in ":8080", Listen listens on all available interfaces instead of just the interface with the given host address.