Introduction to Web Development in Go

In this lesson, explore introduction to web development in go through one small Go program, and connect its output to the language rules behind it.

Go’s net/http package supplies HTTP clients, servers, requests, responses and routing. A handler receives a request and writes a response.

The first example invokes a handler in memory with httptest, so it needs no open port. A real server places the same handler behind a network listener.

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

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() {
	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { fmt.Fprint(w, "Welcome to Go") })
	request := httptest.NewRequest(http.MethodGet, "/", nil)
	recorder := httptest.NewRecorder()
	handler.ServeHTTP(recorder, request)
	fmt.Println("Response:", recorder.Body.String())
}

Output

Response: Welcome to Go

The in-memory request is passed to a handler, which writes a message. The recorder captures that message without a network socket.

• A handler’s response writer is not the same thing as a database connection.
• Use network request tests as well as handler tests when checking real deployments.

Change the handler to return your own greeting and test the result with httptest.

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

You have practiced Introduction to Web Development in Go 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.