What is Preá?

Preá is a web framework for Go. It helps you build HTTP APIs by splitting the application into small, self-contained pieces called preás, and by wiring those pieces together for you.

What you'll learn

• The idea behind Preá, in one page
• The four ideas you will meet everywhere in these docs
• What Preá is good at, and what it leaves to you

The idea

Most applications start small and grow feature by feature. Preá gives each feature a home: a folder with its routes, its rules, its data access and its table. That folder is a preá.

preas/
├── task/      everything about tasks
├── list/      everything about lists
└── health/    GET /health

Inside a preá you write plain Go structs. You don't create them, and you don't pass them around by hand. You declare them, and each one asks for what it needs:

var Module = &core.Module{
	Name:      "task",
	Providers: []any{Repository{}, Service{}, Handler{}},
}

type Service struct {
	Repo *Repository `inject:""` // "I need the task repository"
}

When the app starts, Preá reads these declarations, creates every piece, connects them and checks that nothing is missing. Only then does it start serving requests.

Four ideas

These four ideas show up on almost every page.

Preás. A preá is one feature of your app, declared in module.go. A preá can use another one by importing it, and it decides what it shares by exporting it. Learn about preás →

Components. The structs a preá declares, like its handler, service and repository, are its components. Preá creates one of each and fills the fields you tag with inject:"". Learn about components →

Errors at startup, not in production. A missing dependency, a typo in a model tag or a required setting left empty: Preá finds these when the app starts and stops it with a clear message. A running app has already passed these checks.

Configuration by profile. One base file, config/application.yaml, plus one file per environment: dev, prod and tests. Secrets come from environment variables. Learn about configuration →

What you get

• An HTTP layer with routing, middlewares at three levels, a standard JSON reply format and errors that carry their own HTTP status.
• A database layer for PostgreSQL. Your models describe the tables, Preá generates and applies the migrations, and every model gets a ready-made repository with transactions.
• Safe defaults: CORS, CSRF protection, security headers, server timeouts and a graceful shutdown.
• A CLI that creates projects, generates preás, runs the app with hot reload, migrates the database, runs the tests and builds the binary.

What Preá leaves to you

Preá is pre-alpha (v0.0.x). Some pieces are still on the way:

• Authentication has its building blocks, tokens and password hashing, but no ready-made login flow yet.
• Databases: PostgreSQL is the only one today. A new persistence layer with more databases is coming.
• Validation uses the binding tags of the request structs. A dedicated validation layer is planned.

The What's next page lists what is coming.

Next steps

• Install the CLI
• Create and run your first app