go license key integration (gin or echo)

[abhinav-m22]

I want to contribute a minimal example showing how to handle the full license key lifecycle: activation, validation, and deactivation; using the official Polar Go SDK.

Why this is needed

While the repo has basic checkout examples, it lacks a clear reference for "Product Entitlement." This example will show Go developers how to gate features and secure APIs using Polar’s license key system, unlocking monetization for self-hosted software and restricted tools.

Implementation Details

I’ll use the polar-go SDK to implement a standard service-protection pattern:

1. License Activation Endpoint: A route allowing users to link their purchased license key to their current environment or machine.
2. Validation Middleware: A custom middleware that intercepts requests to protected routes, validating the provided license key using the Polar Go SDK.
3. Deactivation Flow: An endpoint to release an active seat, providing a way for users to migrate their license to a different instance.
4. Webhook Synchronization: Integration that listens for Polar events to automatically track when new licenses are issued or benefits are granted.
5. Configurable Environment: A clear setup for sandbox and production modes via environment variables.

Tech Stack: Go 1.22+, Gin/Echo, Polar Go SDK

[abhinav-m22]

@rishi-raj-jain, would this be a useful addition, and do you prefer Gin for consistency or Echo for variety?