Go generics in action

Generics in Go arrived really late on version 1.18, and with reason, as its usage should be reserved strictly when necessary. There's very few cases when making use of a generic makes sense, for example an assert-like type of function:

func Equal[T comparable](t *testing.T, actual, expected T) {
	t.Helper()

	if actual != expected {
		t.Errorf("got: %v; want: %v", actual, expected)
	}
}

t.Helper() returns the error back up to the caller to avoid showing the file:line error message on this function

A useless example, but that helps explain type restriction:

func SumIntsOrFloats[K comparable, V int64 | float64](m map[K]V) V {
    var s V
    for _, v := range m {
        s += v
    }
    return s
}

Note that comparable is just an interface similar to this one:

type Number interface {
    int64 | float64
}

Which just helps restrict the kind of values this generic can be.