What are generics in Go and how do they work?

Generics (type parameters) were introduced in Go 1.18 and allow writing functions and types that work with any type satisfying a given constraint. Syntax: func Map[T, U any](s []T, f func(T) U) []U. Constraints are interfaces that restrict which types are accepted — the built-in comparable allows ==, and the golang.org/x/exp/constraints package provides Integer, Ordered, etc. You can also write inline union constraints: [T int | float64]. Generics are instantiated at compile time, producing specialized code per type (monomorphization), with some inlining to control binary size. They eliminate many uses of interface{} and unsafe type assertions.