Creational patterns

Create related objects through one factory so whole product families can change together without leaking concrete types.

Separate a multi-step construction workflow from the final representation so the same input can produce different outputs cleanly.

Use constructor functions and small interfaces to select concrete implementations without coupling callers to them.

Clone preconfigured object graphs when copying is simpler or faster than rebuilding the same structure from scratch.

Use sync.Once carefully for one-time initialization, and understand when dependency injection is a better fit.