What does nil mean in golang?

  • For the data types like slice and pointers which "refer" to other types, "nil" indicates that the variable does not refer to an instance (equivalent of null pointer in other languages)
  • It is thee zero value of the variables of type functions, maps, interfaces, channels and structures

nil is also a value but only difference is- it is empty.

In Javascript for the un-initialized variable will be undefined. In the same way Golang has nil as default value for all the un-initalized data types.

In Go, nil is the zero value for pointers, interfaces, maps, slices, channels and function types, representing an uninitialized value.

nil doesn't mean some "undefined" state, it's a proper value in itself. An object in Go is nil simply if and only if it's value is nil, which it can only be if it's of one of the aforementioned types.

An error is an interface, so nil is a valid value for one, unlike for a string. For obvious reasons a nil error represents no error.

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.