Composition-Oriented Programming for Go.

go-composites is a family of small, hand-written building blocks for Go that model values as composites — types assembled by composition and interfaces, not by class hierarchies or inheritance. There are no base classes to extend and no super calls; behaviour is provided by embedding small pieces together and programming against narrow interfaces.

• Interface-first. Every component exposes an exported Interface. Callers depend on the interface, never on the concrete struct. The struct (data) is unexported and constructed through a New(...) function with functional options.
• Composition over inheritance. Richer behaviour is built by holding and delegating to smaller composites, not by subclassing. A String has the pieces it needs; it does not extend a parent.
• No naked objects, no naked errors. Two invariants run through every repo:

Constructors and methods never return a bare nil for an interface. Each interface that can be "empty" carries an IsNull() bool method, and there is a real null-object implementation that answers true. Calling a method on an "absent" value is always safe — you get a well-behaved null object instead of a panic. Real values answer IsNull() bool { return false }.

Fallible operations don't return (value, error) pairs and never panic. They return a Result — a composite that wraps either a payload or an error (itself a null-object-friendly composite). Division by zero, a missing key, or a parse failure produces a Result whose HasError() is true, carrying an Error built with Error.New("..."). Success carries the payload via Result.WithPayload(x).

import (
    Array  "github.com/go-composites/array/src"
    Result "github.com/go-composites/result/src"
)

a   := Array.New()
r   := a.Fetch(0)        // out of range → a Result, not a panic
if r.HasError() {
    // handle r.Error(), which is never nil
}

• Module path: module github.com/go-composites/<repo>.
• Pure Go, CGO_ENABLED=0, builds and tests on all supported architectures.
• 100% statement coverage on library (src) packages — an org hard rule.
• Licensed BSD-3-Clause.

• Landing page: https://go-composites.github.io/
• Documentation: https://go-composites.github.io/docs/