chain-of-responsibility-go

# Chain of Responsibility (Go)

**Why:** Chain of Responsibility lets you pass a request (or context) along a chain of handlers. Each handler decides whether to process it and pass to the next, or short-circuit. You avoid one big function with all steps and keep each step in its own type ([Refactoring.Guru](https://refactoring.guru/design-patterns/chain-of-responsibility)).

**Hard constraints:** Handlers share a single interface (e.g. `Handle(ctx, request)`). Each handler holds a reference to the next; the client composes the chain. A handler either processes and passes, or passes without processing.