Generics in Go — Explained Simply

A hands-on, no-jargon walkthrough of generics in Go: what problem they solve, the syntax, and the patterns you'll actually use. Each topic is a small, runnable Go program with a README that explains the "why," not just the "what" — the code is already self-documenting for that part.

Who this is for

Anyone who knows basic Go (functions, structs, slices, maps) but hasn't written generic code yet — whether you've never touched it, or you've read about it and just want to see it in working programs before using it yourself.

Requirements

Go 1.18 or later (generics were introduced in 1.18). This repo is developed against a recent Go release; nothing here uses anything newer than the standard library's cmp package (Go 1.21+).

How to use this repo

Each numbered folder is a standalone, runnable program. Read its README.md first, then run it and read the output alongside main.go:

go run ./01-why-generics
go run ./02-type-parameters
go run ./03-constraints
go run ./04-generic-structs
go run ./05-map-filter-reduce
go run ./06-data-structures
go run ./07-numeric-toolkit

They're numbered in the order they're meant to be read — each one builds on ideas from the last.

Contents

#	Topic	What you'll learn
01	Why Generics?	The problem generics solve: code duplication vs. losing type safety with interface{}.
02	Type Parameters	The [T Constraint] syntax, type inference vs. explicit instantiation, any vs comparable.
03	Constraints	Writing custom constraints with | unions, the ~ (approximation) element, and the standard library's cmp.Ordered.
04	Generic Structs	Type parameters on structs, methods on generic types, and why methods can't add new type parameters.
05	Map, Filter, Reduce	Generic, reusable slice transformations — the pattern you'll reach for constantly.
06	Data Structures	A generic Stack[T any] and Set[T comparable] — picking the constraint that matches what the code needs.
07	Numeric Toolkit	Min/Max/Sum/Average, and why picking the narrowest correct constraint matters.

Verify everything builds

go build ./...
go vet ./...

Contributing

Found something unclear or have another generics pattern worth a topic folder? Issues and PRs are welcome .The goal of this repo is to be the easiest possible to Go generics, so clarity beats cleverness every time.