Creating an HTTP Server

In this lesson, explore creating an http server through one small Go program, and connect its output to the language rules behind it.

http.Server listens for connections, calls a handler for each request, and manages request lifecycles. Production servers should set sensible timeouts and plan graceful shutdown.

The primary example demonstrates a handler without opening a socket; the additional snippet shows the real server call.

Follow this diagram before executing the example. Check where a value or decision changes what runs next.

Actual localhost server

package main
import (
    "fmt"
    "log"
    "net/http"
    "time"
)
func main() {
    mux := http.NewServeMux()
    mux.HandleFunc("GET /", func(w http.ResponseWriter, r *http.Request) { fmt.Fprint(w, "hello") })
    server := &http.Server{Addr: ":8080", Handler: mux, ReadHeaderTimeout: 5*time.Second}
    log.Fatal(server.ListenAndServe())
}

Run with go run . and open http://localhost:8080/. The process keeps running until stopped. For shutdown, call server.Shutdown(ctx) after a termination signal.

This example is a complete program. Save it as main.go or paste it into the Go Playground.

Go code

package main

import (
	"fmt"
	"net/http"
	"net/http/httptest"
)

func main() {
	mux := http.NewServeMux()
	mux.HandleFunc("GET /", func(w http.ResponseWriter, r *http.Request) { fmt.Fprint(w, "Go server is ready") })
	rec := httptest.NewRecorder()
	mux.ServeHTTP(rec, httptest.NewRequest("GET", "/", nil))
	fmt.Println(rec.Body.String())
}

Output

Go server is ready

NewServeMux registers a GET endpoint. The example sends a request through the mux and captures the handler output.

• http.ListenAndServe blocks while the server runs.
• Use a dedicated http.Server with timeouts and a controlled shutdown path in production.

Run the server snippet locally, visit /, and try a request with the wrong method.

Tip: Edit the example above, predict the output, and run the modified code to test your reasoning.

You have practiced Creating an HTTP Server in a small, self-contained program. The important habit is to predict what runs, inspect the actual output and distinguish the language rule from the particular example.

Before continuing, make sure you can explain the program to someone who has not seen it, including the line that changes its result.