Directory Architecture

Follows golang-standards/project-layout.

.
├── build/
│   └── package/
│       └── build.sh              # Lambda binary build script
├── cmd/
│   ├── lambda/
│   │   └── main.go               # Lambda entry point
│   └── server/
│       └── main.go               # Local development HTTP server (:8080)
├── deployments/
│   └── Dockerfile                # Lambda container image build definition
├── docs/                         # Documentation submodule
├── internal/
│   ├── handler/
│   │   └── upload.go             # Request parsing, validation, S3 save call
│   └── storage/
│       └── s3.go                 # S3 PutObject wrapper
├── api/                          # swaggo-generated files (auto-generated, do not edit)
├── go.mod
├── go.sum
└── Makefile

Directory Roles

Directory	Role
build/package/	Cross-compilation script for Lambda
cmd/lambda/	Lambda entry point. Assembles dependencies only; contains no business logic
cmd/server/	Local development entry point. Starts Echo directly on :8080
deployments/	Dockerfile for Lambda container image
docs/	Project documentation (submodule)
internal/handler/	Parses upload requests, validates input, and generates responses
internal/storage/	Abstracts S3 operations (used from handler via Storer interface)
api/	OpenAPI spec and Swagger UI assets generated by swaggo (auto-generated, do not edit)

Dependency Graph

cmd/lambda  ──┐
              ├──▶ internal/handler ──▶ internal/storage
cmd/server  ──┘

internal/handler accesses internal/storage through the Storer interface. The implementation is injected in the cmd layer, and can be swapped for a mock in tests.