Short declaration :=

Learn short variable declaration with :=.

Short declaration :=

The short way to declare a variable inside a function in Go is the := operator. Writing x := 5 both creates the variable and infers its type from the right side.

This operator works only inside functions; it cannot be used at package level. var works everywhere, while := is a shortcut for functions.

A variable declared with := can later be reassigned with =. Reusing := with the same name is a compile error unless at least one new variable appears.

The := vs = difference

:= declares a new variable and assigns a value. = assigns to an existing variable. Mixing them up is a common mistake.

For example x := 5 creates x; later x = 10 changes its value. Writing x := 10 again raises a 'no new variables' error.

For functions returning multiple values, a, b := f() is very handy; both variables are declared in one line.

Exercise := and =

Create the variable with sayac := 1, then update it twice with =: first sayac = sayac + 1, then sayac = sayac * 10. Print the result.

Show example solution

package main

import "fmt"

func main() {
    sayac := 1
    sayac = sayac + 1
    sayac = sayac * 10
    fmt.Println(sayac)
}

Test yourself

Where can the := operator not be used?
- Inside a function
- At package level
- Inside a loop
- In an if block
Show answer

At package level — := is only for functions, not package level.

Short assignment

To assign 5 to x with the short form:
x ____ 5

Show answer

To assign 5 to x with the short form:
x := 5

Match the operators

:=

Short decl
=

Assignment
==

Equality
var

Long decl

Next lesson: const and iota

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