Generics – Type Parameters (Go 1.18+)

Introducing Generics

This lesson explains the main concept clearly with beginner-friendly examples and background so you can learn why the code works.

Generics let you write reusable data structures without sacrificing type safety.

// A generic slice‑type that can hold any ordered type
func Index[T comparable](slice []T, value T) int {
    for i, v := range slice {
        if v == value { return i }
    }
    return -1
}

Constraints

type Number interface{ ~int | ~int64 | ~float64 }

func Sum[T Number](vals []T) T {
    var total T
    for _, v := range vals { total += v }
    return total
}

Using generic types in structs

type List[T any] struct { items []T }

func (l *List[T]) Add(v T) { l.items = append(l.items, v) }