Selectors

For a primary expression x that is not a package name, the selector expression

x.f

denotes the field or method f of the value x (or sometimes *x; see below). The identifier f is called the (field or method) selector; it must not be the blank identifier. The type of the selector expression is the type of f. If x is a package name, see the section on qualified identifiers.

This section is mostly definitional. But let’s illustrate. Given the following code:

type Person struct {
  Name string
}

func (p *Person) Greet() {
  fmt.Println("Hello,", p.Name)
}

var p = Person{Name: "Bob"}

These would be examples of some primary expressions of the form described:

p.Name  // `Name` is a field selector, with type `string`
p.Greet // `Greet` is a method selector, with type `func()`

Note that the field or method selector cannot be blank. Blank identifiers are asymmetric in this sense:

type Phantom struct {
  _ string // Blank identifier is valid as a field name
}

var p Phantom

p._ // Invalid: However, you cannot reference the blank identifier with a selector. That's kind of the point...

Quotes from The Go Programming Language Specification Version of August 2, 2023