go-springfield-bank

Go Springfield Bank

Go Springfield Bank is a simple digital bank API. Its main purpose is to transfer amounts between internal accounts.

Written in Golang, this project aims to follow Go best practices and the clean architecture for better maintainability, extensibility and testability.

Table of Contents

• Features
• Demo / Deployment
• Running
• Endpoints
• Development
• Environment variables
• References

Features

• RESTful endpoints using julienschmidt/httprouter
• JWT-based authentication using golang-jwt/jwt
• Postgres database connection pool using jackc/pgx
• Database migration golang-migrate/migrate
• Environment variables configuration using ilyakaznacheev/cleanenv
• Structured logging with contextual information zerolog
• Error handling with proper HTTP status code
• Idempotent requests
• Metrics/health endpoints with heptiolabs/healthcheck
• OpenAPI/Swagger 2.0 documentation generated with swaggo/swag
• Integration tests with the help of ory/dockertest

Demo / Deployment

A GitHub Action is configured to compile, test, build a docker image and deploy to Heroku.

The application is accessible at https://go-springfield-bank.herokuapp.com/.

Running

You can quickly build and run the application with its dependencies with this command ( requires docker-compose):

make start

You can stop it with:

make stop

Endpoints

The complete API documentation is available at /swagger.

Demo: https://go-springfield-bank.herokuapp.com/swagger

Accounts

• POST /accounts - Create an account
  • accepts the X-Idempotency-Key header.
• GET /accounts - Fetch all the accounts
• GET /accounts/:id/balance - Get the balance of an account

Authentication

• POST /login - Authenticate the user and return the access token
  • The returned access_token must be sent in the Authorization header for "protected" endpoints using the format Bearer <access_token>.

Transfers

• POST /transfers - Protected. Transfer money to another account
  • requires the Authorization header.
  • accepts the X-Idempotency-Key header.
• GET /transfers - Protected.Fetch all the transfers related to the logged-in account
  • requires the Authorization header.

Idempotent requests

Idempotent requests are very useful to prevent accidentally processing the same request/operation twice.

Some endpoints accept the special header X-Idempotency-Key.

The client should send a unique key per operation, and if retrying the same operation with the same values it should send the same key. This application will cache the result of that operation and if another request with the same X-Idempotency-Key arrives the cached result will be returned.

Redis is used to cache the idempotent responses.

Metrics/Health

The monitoring endpoints listen on a different port for security reasons. The monitoring port number can be changed using the MONITORING_PORT environment variable.

• GET /metrics - Prometheus metrics
• GET /ready - Readiness endpoint
• GET /live - Liveness endpoint

Development

Architecture and data flow

Here's a simple sequence diagram that shows the roles of Controllers, Use Cases and Repositories, and how they interact with each other:

Postgres and Redis servers

The application depends on Postgres and Redis servers.

You can get a Postgres and a Redis server up and running quickly by running ( requires docker-compose):

make dev-up

You can shut them down later by running:

make dev-down

Setup

You can get the application dependencies by running (requires go 1.11+):

make setup

Tests

You can easily run the tests with:

make test

Environment variables

Check definitions and examples of configuration variables used by this app at config/.env.example .

References

Project layout

• https://github.com/golang-standards/project-layout

Architecture

• https://blog.cleancoder.com/uncle-bob/2012/08/13/the-clean-architecture.html
• https://pusher.com/tutorials/clean-architecture-introduction
• https://dave.cheney.net/2016/08/20/solid-go-design
• https://medium.com/@jfeng45/go-micro-service-with-clean-architecture-application-layout-e6216dbb835a
• https://developpaper.com/go-microservices-with-clean-architecture-program-structure/
• https://medium.com/gdg-vit/clean-architecture-the-right-way-d83b81ecac6
• https://threedots.tech/post/ddd-cqrs-clean-architecture-combined/
• https://hackernoon.com/golang-clean-archithecture-efd6d7c43047

Error handling

• https://medium.com/rungo/error-handling-in-go-f0125de052f0
• https://medium.com/spectro-cloud/decorating-go-error-d1db60bb9249

Web server

• https://marcofranssen.nl/go-webserver-with-graceful-shutdown/
• https://getgophish.com/blog/post/2018-12-02-building-web-servers-in-go/

Authentication and JWT

• https://dev.to/stevensunflash/a-working-solution-to-jwt-creation-and-invalidation-in-golang-4oe4
• https://learn.vonage.com/blog/2020/03/13/using-jwt-for-authentication-in-a-golang-application-dr/
• https://dev.to/omnisyle/simple-jwt-authentication-with-golang-part-3-1ja3
• https://codeburst.io/using-jwt-for-authentication-in-a-golang-application-e0357d579ce2
• https://hackernoon.com/creating-a-middleware-in-golang-for-jwt-based-authentication-cx3f32z8

Tests

• https://dev.to/quii/learn-go-by-writing-tests-structs-methods-interfaces--table-driven-tests-1p01
• https://povilasv.me/go-advanced-testing-tips-tricks/
• https://dev.to/johndoe/integration-tests-with-dockertest-and-go-3eda
• https://www.ory.sh/dockertest-gaen-google-apple-exposure-notification-covid-19/
• https://blog.questionable.services/article/testing-http-handlers-go/
• https://medium.com/easyread/integration-test-database-in-golang-using-dockertest-59ed3b35240e
• https://jonnylangefeld.com/blog/how-to-write-a-go-api-part-3-testing-with-dockertest

Best practices and tips

• https://github.com/golang/go/wiki/CodeReviewComments
• https://github.com/uber-go/guide/blob/master/style.md
• https://12factor.net/
• https://peter.bourgon.org/go-in-production/
• http://devs.cloudimmunity.com/gotchas-and-common-mistakes-in-go-golang/
• https://blog.learngoprogramming.com/gotchas-of-defer-in-go-1-8d070894cb01
• https://blog.learngoprogramming.com/5-gotchas-of-defer-in-go-golang-part-ii-cc550f6ad9aa
• https://blog.learngoprogramming.com/5-gotchas-of-defer-in-go-golang-part-iii-36a1ab3d6ef1
• https://blog.learngoprogramming.com/go-functions-overview-anonymous-closures-higher-order-deferred-concurrent-6799008dde7b

Git

• https://www.conventionalcommits.org/en/v1.0.0/
• https://medium.com/desenvolvendo-com-paixao/otimize-seu-reposit%C3%B3rio-git-utilizando-o-arquivo-gitattributes-82a23517dcd0

Idempotent requests

• https://stripe.com/docs/api/idempotent_requests
• https://ieftimov.com/post/understand-how-why-add-idempotent-requests-api/
• https://goenning.net/2017/03/18/server-side-cache-go/