Your First Module

Status: Placeholder - Content coming soon

Prerequisites: Quick Start Guide, Go 1.21+ installed

Planned Content

This tutorial will teach you how to create a complete Go module from scratch in an r2r monorepo.

What You'll Learn

Create a simple Go module (hello-world-service)
Write table-driven unit tests (*_test.go)
Define the module contract in .r2r/eac/repository.yml
Understand module types, dependencies, and artifacts
Build and test with r2r build and r2r test
Verify module registration with r2r show modules

Tutorial Structure

Set up module directory structure
Create go/hello-world-service/ directory
Initialize Go module with go mod init
Understand Go module organization
Write the implementation
Create service.go with a simple greeting function
Follow Go idiomatic conventions
Keep it simple and focused
Write unit tests
Create service_test.go
Implement table-driven tests
Run tests with go test
Register the module
Add module contract to .r2r/eac/repository.yml
Define module type, dependencies, and build configuration
Understand contract schema
Build and test with r2r
Build: r2r build hello-world-service
Test: r2r test hello-world-service
Inspect artifacts: r2r show artifacts hello-world-service
Understand module metadata
Module types (go-app, go-lib, go-tool, etc.)
Dependencies between modules
Build artifacts and their purpose

Example Module

The tutorial will create a simple greeting service:

package greet

func Greet(name string) string {
    if name == "" {
        return "Hello, Guest!"
    }
    return fmt.Sprintf("Hello, %s!", name)
}

With comprehensive table-driven tests and proper error handling.

Key Concepts Covered

Go module structure in monorepo
Module contracts and registration
Table-driven testing pattern
Build artifacts and dependencies
r2r build and test commands

Next Steps

After completing this tutorial, you'll understand module fundamentals. Continue to Understanding Test Suites to learn about test levels and when to use each.

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