IBM fp-go is a comprehensive functional programming library for Go, heavily inspired by fp-ts (TypeScript). It provides a wide range of algebraic abstractions including Option, Either, Result, IO, Reader, State, Writer, and their monad transformer stacks (IOEither, ReaderIOEither, ReaderIOResult, StateReaderIOEither, etc.). The library employs Go generics to simulate higher-kinded types and includes optics (lenses, prisms, isomorphisms, traversals), lazy iterators, retry policies, resource management via Bracket, dependency injection with Reader, and code generation tools. It also offers idiomatic Go wrappers that return (A, error) tuples while preserving functional composition. The codebase is split into two parallel module paths (root and v2/), with v2 representing a newer generation requiring Go 1.24+ and adding result types, effect packages, and context-aware variants. While highly engineered and feature-rich, the dual tree structure, some incomplete components, and non-standard pragmas introduce maintenance complexity.