Identifiers in Go Language

Identifiers are the names given to program elements such as variables, functions, constants, packages and types. They help identify and access different parts of a Go program.

For example, in the following program, main is the package name, main() is the function name and name is the variable name.

package main

import "fmt"

func main() {
    var name = "Maria"
    fmt.Println(name)
}

Maria

Types of Identifiers

Identifiers can be used for different program elements in a Go program, such as:

• Variable names: age, name, totalMarks
• Function names: main(), display(), calculateSum()
• Constant names: PI, MAX_SIZE, siteName
• Package names: main, fmt, math
• Type names: Student, Employee, Person

package main

import "fmt"

const siteName = "GeeksforGeeks"

type Student struct {
	Name string
}

func display() {
	fmt.Println(siteName)
}

func main() {
	var age = 20
	display()
	fmt.Println(age)
}

GeeksforGeeks
20

Here:

• age is a variable identifier.
• display is a function identifier.
• siteName is a constant identifier.
• main and fmt are package identifiers.
• Student is a type identifier.

Rules for Naming Identifiers

A valid Go identifier must follow these rules:

• It must start with a letter (A-Z or a-z) or an underscore (_).
• It can contain letters, digits (0-9) and underscores.
• It cannot start with a digit.
• Identifiers are case-sensitive.
• Go keywords cannot be used as identifiers.

Valid Identifiers

name
_name
user123
total_marks
Geeks

Invalid Identifiers

123name
if
for
switch

Case Sensitivity in Identifiers

Go treats uppercase and lowercase letters as different identifiers.

package main

import "fmt"

func main() {
    age := 20
    Age := 25

    fmt.Println(age)
    fmt.Println(Age)
}

20
25

Explanation: Here, age and Age are two different identifiers.

Blank Identifier

The underscore (_) is known as the blank identifier. It is used when a value is required syntactically but does not need to be stored.

package main

import "fmt"

func main() {
    _, b := 10, 20
    fmt.Println(b)
}

20

Explanation: The value 10 is assigned to _ and ignored.

Exported Identifiers

Identifiers that begin with an uppercase letter are called exported identifiers. They can be accessed from other packages.

package mathutil
var TotalMarks = 500

Since TotalMarks starts with an uppercase letter, it can be used by other packages.

Non-Exported Identifier

package mathutil
var totalMarks = 500

Since totalMarks starts with a lowercase letter, it can only be accessed within the same package.