Go Functional Options

This teaches Claude the functional options pattern for Go constructors, the approach where you pass variadic Option types instead of sprawling parameter lists. It's well suited for any New* function with three or more optional parameters, or APIs that might grow over time. The skill covers the full implementation (unexported options struct, Option interface with unexported apply method, With* constructors) and includes a comparison table against config structs so you know when to use which. It's opinionated about preferring interfaces over closures for testability, and the examples are lifted from Uber's style guide. Good reference material if you're tired of constructors that take eight booleans.