Multiple HTTP servers

Source: https://github.com/go-monk/multiple-http-servers

In this post, we’ll build a command-line Go program that spins up multiple HTTP servers concurrently, each listening on its own port and serving a simple response. Usually you need just one server so it may seem like an odd thing to do at first glance. However it’s a practical way to play with and understand concurrency and the net/http standard library.

We’ll write a Go program named multiserv that:

• Accepts a number n from the command line

• Starts n HTTP servers, each listening on localhost port above 1023

• Assigns each server its own ServeMux and a handler that responds with its server number

We create separate ServeMux instances for each server:

func newMuxers(n int) []*http.ServeMux {
	muxers := make([]*http.ServeMux, n)
	for i := range n {
		muxers[i] = http.NewServeMux()
	}
	return muxers
}

Each handler is just an int, but by defining a method on it, it satisfies the http.Handler interface:

type handler int

func (h handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "hello from handler %d", h)
}

This is a neat trick in Go — using a primitive type (like int) and giving it behavior via methods.

Run the program and test each server:

go run multiserv.go 3

Then in another terminal:

$ curl localhost:1024
hello from handler 0
$ curl localhost:1025
hello from handler 1
$ curl localhost:1026
hello from handler 2

Running multiple HTTP servers can be useful in:

• Load testing: Simulate multiple nodes with lightweight stubs.

• Multi-tenancy demos: Each port could represent a different tenant.

• Local sharding: Simulate partitioned services.

• Teaching concurrency: Excellent for understanding goroutines and handler isolation.

This tiny multiserv tool may not seem like much, but it encapsulates several core ideas in Go:

• Concurrency with goroutines

• Safe closure handling

• HTTP routing with ServeMux

• Interface satisfaction with custom types

It’s a solid building block for more advanced server architectures or just a neat utility to throw in your developer toolbox.