URL Shortener

cd src/url_service/terraform
terraform init -backend-config="env/local-dev/env.tfbackend" -reconfigure
terraform plan -var-file="env/local-dev/env.tfvars"
terraform apply -var-file="env/local-dev/env.tfvars"

How to create a new Lambda function

# Create a new folder under src/url_service/, e.g., create_short_url
mkdir ./src/url_service/create_short_url

# cd src/url_service/<function_name>
cd ./src/url_service/create_short_url

# initialize go module github.com/aws-educate-tw/url-shortener/src/<service>/<function_name>
go mod init github.com/aws-educate-tw/url-shortener/src/url_service/create_short_url

# add aws-lambda-go dependency
go get github.com/aws/aws-lambda-go/lambda

# tidy up dependencies
go mod tidy

# Create directory structure for Hexagonal Architecture
mkdir -p cmd internal/config internal/domain internal/service internal/adapters/handler internal/adapters/repository

# create main.go in the correct location
touch cmd/main.go

# create Dockerfile
touch Dockerfile

Project Structure (Hexagonal Architecture)

We follow the Hexagonal Architecture (Ports and Adapters) for our Lambda functions to ensure testability and separation of concerns.

src/url_service/<function_name>/
├── cmd/
│   └── main.go              # Entry point (Wiring everything together)
├── internal/
│   ├── config/              # Configuration loading (Env vars)
│   │   └── config.go
│   ├── domain/              # Pure business logic & Interfaces
│   │   ├── model.go         # Entities (e.g., ShortURL)
│   │   └── repository.go    # Interfaces (Output Ports)
│   ├── service/             # Application Logic (Use Cases)
│   │   └── service.go       # Business flow implementation
│   └── adapters/            # Infrastructure implementations
│       ├── handler/         # Lambda Handler (Primary Adapter)
│       │   └── lambda.go
│       └── repository/      # Database Implementation (Secondary Adapter)
│           └── dynamodb.go
├── go.mod
├── go.sum
└── Dockerfile

Layer Responsibilities

1. cmd/main.go: The Composition Root. It loads config, initializes adapters, injects dependencies into the service, and starts the Lambda handler.
2. internal/domain: Contains pure business entities and interfaces (Ports). It has NO external dependencies (no AWS SDK, no HTTP).
3. internal/service: Implements the business use cases. It depends only on the Domain layer.
4. internal/adapters: Contains the implementation of interfaces (e.g., DynamoDB repository) and the entry point handler (Lambda).
5. internal/config: Handles loading configuration from environment variables.