The application is based from a Go article. Changed the app with some refactorings, and to make each component easier to understand.
The Ports & Adapters Architecture (aka Hexagonal Architecture) was thought of by Alistair Cockburn and written down on his blog in 2005. This is how he defines its goal in one sentence:
Allows an application to equally be driven by users, programs, automated test or batch scripts, and to be developed and tested in isolation from its eventual run-time devices and databases.
The main idea in this architecture is to separate the concerns, each component has a well-defined purpose. Focus on the core business and the external services will plug and play with the application through ports and adapters.
P.S. The hexagonal architecture is agnostic of the programming language.
A port is a consumer agnostic entry and exit point to/from the core business. In many languages, it will be an interface. For example, it can be an interface to perform searches in a search engine.
Adapters can be external services that wants to communicate with the application business logic.
Example 1: An input adapter could be a web interface. When a user clicks a button, the web adapter calls a certain input port to communicate with the core.
Example 2: An output adapter adapters are called by our core business, for instance, persisting data into a database.
Run the app:
go build hexagonal/cmd/serve
Test:
go test hexagonal/tests