Go Interfaces

Covers the practical side of Go interfaces: where to define them (consumer's package, not producer's), when to use pointer versus value receivers, and how to write compile-time satisfaction checks with the `var _ I = (*T)(nil)` pattern. Includes a script that scans your codebase for missing interface compliance checks, which is genuinely useful for catching drift. The "accept interfaces, return concrete types" guidance is the most important bit here, and it's explained clearly with good and bad examples. Also covers type assertions, type switches, and embedding gotchas. If you're writing testable Go or designing package boundaries, this gives you the idioms you need without the usual blog post fluff.