Complete Go Web Application

Learn complete go web application through an executable example, then connect the small demonstration to production code.

A small web application combines HTTP routing, form handling, templates, validation and state. The project demonstrates the full request–response path in one standard-library program and uses a local test server.

This is a functioning in-memory teaching application. Production readiness additionally needs persistent storage, authentication, CSRF protection, access controls, monitoring and deployment configuration.

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

Suggested project layout: cmd/web/main.go, internal/tasks/service.go, internal/tasks/store.go, internal/web/handlers.go and template files. Replace the httptest server with a configured http.Server for deployment.

Quality gates: cover CRUD, invalid inputs, concurrent requests, CSRF/session behavior, SQL migrations, graceful shutdown, logging and accessibility before claiming production readiness.

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

Go code

package main

import (
	"fmt"
	"html/template"
	"io"
	"net/http"
	"net/http/httptest"
	"net/url"
	"strings"
	"sync"
)

type App struct {
	mu    sync.Mutex
	tasks []string
}

func (a *App) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if r.Method == http.MethodPost {
		if err := r.ParseForm(); err != nil {
			http.Error(w, "invalid form", 400)
			return
		}
		title := strings.TrimSpace(r.Form.Get("title"))
		if title == "" {
			http.Error(w, "title required", 400)
			return
		}
		a.mu.Lock()
		a.tasks = append(a.tasks, title)
		a.mu.Unlock()
		http.Redirect(w, r, "/", http.StatusSeeOther)
		return
	}
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", 405)
		return
	}
	a.mu.Lock()
	tasks := append([]string(nil), a.tasks...)
	a.mu.Unlock()
	page := template.Must(template.New("index").Parse("<h1>Tasks</h1>{{range .}}<p>{{.}}</p>{{end}}"))
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := page.Execute(w, tasks); err != nil {
		return
	}
}
func main() {
	server := httptest.NewServer(&App{})
	defer server.Close()
	response, err := http.PostForm(server.URL, url.Values{"title": {"Learn Go"}})
	if err != nil {
		panic(err)
	}
	body, err := io.ReadAll(response.Body)
	response.Body.Close()
	if err != nil {
		panic(err)
	}
	fmt.Println("Status:", response.StatusCode)
	fmt.Println("Task visible:", strings.Contains(string(body), "Learn Go"))
}

Output

Status: 200
Task visible: true

POST validates and adds Learn Go, redirects to GET /, and the HTTP client follows the redirect. The template renders the saved task. The printed checks confirm a 200 final response and visible task text.

• For a real multi-user app, store data persistently and authorize access to each user’s tasks.
• Add CSRF protection, body limits, server timeouts, error logging and safe database operations before public deployment.

Extract service and storage packages, add SQL persistence and tests, then deploy with readiness checks and graceful shutdown.

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

You have practiced Complete Go Web Application 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.