The post outlines a detailed guide on how to authenticate a Golang CLI application using FusionAuth's OAuth2 Device Code Grant, particularly useful for devices lacking a user-friendly interface for logging in, such as smart TVs or Raspberry Pi. It begins by setting up the necessary environment, including installing Golang, configuring FusionAuth on a local machine, and creating a FusionAuth application and user. The core of the guide focuses on the implementation of a CLI app called "getgif," which uses commands like `login`, `fetch`, and `logout` to authenticate users, fetch gifs from Giphy, and manage user sessions. The process involves initiating a Device Code grant, displaying a user code for authentication, polling the FusionAuth server, and finally obtaining a JWT Access Token that allows the app to retrieve and save user information. The post concludes by encouraging further exploration of FusionAuth's capabilities and the Golang client library.