Tour of Go 2.0

Nil slices

The zero value of a slice is nil. A nil slice has no underlying array, and both its length and capacity are 0.

You can pass a nil slice to append — it works fine. But you can’t index into it.

main.go ▶ Run in Playground 
package main

import "fmt"

func main() {
	var s []int
	fmt.Println(s, len(s), cap(s))
	if s == nil {
		fmt.Println("nil!")
	}
}