Generics in Go

Go is a language that is notorious for its lack of Generics, a rudimentary programming feature that is widely adopted in other famous languages all this while, until the release of Go version 18 that has finally shipped along with Generics into its codebase.

Updating Go

First thing that you will need to do is to update your Go version to at least 18 if you haven't already by running the Go install command from an elevated command line such as the Powershell on Windows.

Chocolatey, a package manager for Windows are used for the demonstration for both the installation as well as the update for Go.

# Install
choco install golang -y

# Update
choco upgrade golang -y

For WSL users, you may install the latest version by running the following command.

go install golang.org/dl/go1.18@latest

Alternatively, you may consider using Go version manager (GVM) for managing different Go versions in the Linux system as it is very easy to use and has a striking resemblance on how the Node version manager (NVM) operates.

The updating guides for Linux can also be found here on the instruction gist by Nikhita.

Generics syntax

Typically generics in other programming languages are denoted by angle brackets such as <T> where T is the generic type but it's a bit different in Go as it uses square brackets [] instead.

This example shows the generic type T is unbounded as it can take in basically every type that Go supports.

func genericFunc[T any](item T) {
    fmt.Println("My generic variable: ", item)
}

The equivalence in C# is as follows.

public void genericFunc<T>(T item) {
    Console.WriteLine("My generic variable: ", item);
}

The function below takes in a custom type called item that can either be int64 or float32 only. This pretty much resembles the union type in Typescript.

func genericFunc[T int64 | float32](item T) {
    fmt.Println("My generic variable: ", item)
}

Grouping types

If you would like to implement a generic function that takes in a multitude of types but not any, you can group them into a union type by using interface.

type Integer interface {
    int8 | int16 | int32 | int64
}

You will now be able to use all the integer types in the function.

func genericFunc[T Integer](item T) {
    fmt.Println("My generic variable: ", item)
}

There you have it, generics in Go. Not quite the same way that we used to in other languages, but it is how it is.