What does nil mean in golang?

Question

There are many cases using nil in golang. For example:

func (u *URL) Parse(ref string) (*URL, error) {
    refurl, err := Parse(ref)
    if          


        

Answer 1

nil in Go is simply the NULL pointer value of other languages.

You can effectively use it in place of any pointer or interface (interfaces are somewhat pointers).

You can use it as an error, because the error type is an interface.

You can't use it as a string because in Go, a string is a value.

nil is untyped in Go, meaning you can't do that:

var n = nil

Because here you lack a type for n. However, you can do

var n *Foo = nil

Note that nil being the zero value of pointers and interfaces, uninitialized pointers and interfaces will be nil.