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Profile picture Oscar Corner

Building a go App

/ 5 min read

Building a go app.

All the code can be find in the following repo in the infra cluster folder.

After reading and getting through the go books about web apps let’s go and let’s go further, I wanted to apply my learnings by building something myself.

Demonstration of how the app works

go app

Why go?

Having previously learned Python, I found Go’s simplicity and explicitness refreshing. While it requires more manual handling, it aligns better with my preferences, allowing for a deeper understanding and precise control over the application.

Why Postgres?

I wanted to a project that wasn’t a simple hello world, that I could demonstrate the deployment of a more complex app and having more elements and not just a simple API. So I decided to add a DB, Postgres seems a suitable option, but MySQL would be equally good.

Why htmx and Tailwindcss?

I never dabbled much in the frontend world, and it felt that this was the easiest way to achieve an app that has a nice UI and reactivity.

Project Structure

├── cmd
│   ├── handlers_test.go
│   ├── handlres.go
│   ├── main.go
│   ├── templates.go
│   └── validate.go
├── docker-compose.yaml
├── Dockerfile
├── go.mod
├── go.sum
├── internal
│   └── data
│       ├── main.go
│       ├── main_test.go
│       └── testutils.go
├── Makefile
├── migrate
│   ├── 0001_create_table.sql
│   ├──
│   └── migrationsfs.go
├── migrations
│   └── migrate.go
│   │      ├── package.json
├── package-lock.json
├── public
│   └── tailwind.css
├── static
│   ├── edit-form.html
│   ├── htmx.min.js
│   ├── input.css
│   ├── static.go
│   └── tailwind.css
├── tailwind.config.js
├── templates
│   ├── edit-form.html
│   ├── efs.go
│   ├── index.html
│   └── table.html
── todo

Code Highlights:

All the routes for the crud operations

func serverRoutes(app *application) {
	// use embed for the static files
	assets, _ := static.Assets()
	fs := http.FileServer(http.FS(assets))
	http.Handle("/static/", http.StripPrefix("/static/", fs))
	http.HandleFunc("/", app.GetTodosHandler)
	http.HandleFunc("/health", app.Health)
	http.HandleFunc("/new-todo", app.InsertTodoHandler)
	http.HandleFunc("/delete/", app.RemoveTodoHandler)
	http.HandleFunc("/update/", app.MarkTodoDoneHandler)
	http.HandleFunc("/modify/", app.EditHandlerForm)
	http.HandleFunc("/edit/", app.EditTodoHandler)

Main struct to define the CRUD operations.

type TodoModel interface {
	InsertTodo(args string) error
	GetTodo() ([]Todo, error)
	RemoveTodo(id int) error
	MarkTodoAsDone(id int) error
	EditTodo(id int, task_name string) error
	SelectTodo(id int) (*Todo, error)
	GetLastInsertedTodo() (*Todo, error)
	Ping(ctx context.Context) error
type Todo struct {
	Id        int
	Task_name string
	Status    bool

type Postgres struct {
	DB *pgxpool.Pool

This allows for an easy way to call this operations and makes testing very effortless.

Handler Example:
func (app *application) UpdateHomeHandler(w http.ResponseWriter) {
	todos, err := app.todos.GetTodo()
	if err != nil {
		log.Fatal("failed to updateHome while getting todos")
	data := TodoData{
		Todos: todos,
	err = renderTemplate(w, "index.html", data)
	if err != nil {
		log.Fatal("failed to updateHome while rendering template")
Test Example:
func testInsertTodo(t *testing.T, pg *Postgres) {
	args := "Test Todo"
	err := pg.InsertTodo(args)
	if err != nil {
		t.Fatalf("InsertTodo failed: %v", err)

	lastTodo, err := pg.GetLastInsertedTodo()
	if err != nil {
		t.Fatalf("Error getting last inserted todo: %v", err)

	assertEqual(t, lastTodo.Task_name, args, "Task_name mismatch")
	assertEqual(t, lastTodo.Status, false, "Status mismatch")

Main functions that creates the servers makes the migrations and makes sure that we set up the db properly

func main() {
	ctx := context.Context(context.Background())
	dsn := getdgburl()
	err := mg.MigrateDb(dsn)
	if err != nil {
		log.Fatal("Db is not set up properly chekc the env vars")
	if err != nil {
		log.Fatal("Failed to migrate DB")
	db, err := internal.NewPool(ctx, dsn)
	if err != nil {
		log.Fatal("Failed to set up DB")
	app := &application{
		todos: &internal.Postgres{DB: db},
	err = http.ListenAndServe(":3000", nil)
	if err != nil {
		log.Fatal("Unable to start http server")
	log.Println("Server running on port 3000")

About testing:

For testing I’ve build with the help of TestContainers, a way that will create a postgres container, apply the migrations, and then we can run the tests directly on the db.

They might run a bit slower, than using mocks, but I think is better to run against the same db as prod.

func SetUpTestDB() *TestDB {
	ctx, cancel := context.WithTimeout(context.Background(), time.Second*60)
	container, dbInstance, dbAddr, err := createContainer(ctx)
	if err != nil {
		log.Fatal("Failed to set up test ", err)
	println("Im failing at main func")
	err = mg.MigrateDb(dbAddr)
	if err != nil {
		log.Fatal("Failed to perform db migration", err)
	return &TestDB{
		container:  container,
		DBInstance: dbInstance,
		DbAddress:  dbAddr,
func createContainer(ctx context.Context) (testcontainers.Container, *pgxpool.Pool, string, error) {
	env := map[string]string{
		"POSTGRES_PASSWORD": password,
		"POSTGRES_USER":     user,
		"POSTGRES_DB":       db,
	port := "5432/tcp"

	req := testcontainers.GenericContainerRequest{
		ContainerRequest: testcontainers.ContainerRequest{
			Image:        "postgres:16.1",
			ExposedPorts: []string{port},
			Env:          env,
			WaitingFor:   wait.ForLog("database system is ready to accept connections"),
		Started: true,
	container, err := testcontainers.GenericContainer(ctx, req)
	if err != nil {
		return container, nil, "", fmt.Errorf("Failed to start container: %v", err)
	p, err := container.MappedPort(ctx, "5432")
	if err != nil {
		return container, nil, "", fmt.Errorf("failed to get container external port: %v", err)

	log.Println("postgres container ready and running at port: ", p.Port())
	dbAddr := fmt.Sprintf("localhost:%s", p.Port())
	dsn := fmt.Sprintf("postgres://%s:%s@%s/%s?sslmode=disable", user, password, dbAddr, db)
	print("Var for dsn")
	db, err := NewPool(ctx, dsn)
	if err != nil {
		log.Fatal("Failed in pool")
		return container, db, dbAddr, fmt.Errorf("failed to establish database connection: %v", err)
	return container, db, dsn, nil