What does := mean in Go?

Question

I'm following this tutorial, specifically exercise 8:

http://tour.golang.org/#8

---

package main

import "fmt"

func swap(x, y string) (string, string) {
    return y, x
}

func main() {
    a, b := swap("hello", "world")
    fmt.Println(a, b)
}

Specifically what does the := mean? Searching for Go documentation is very hard, ironically.

Answer 1

A short variable declaration uses the syntax:

ShortVarDecl = IdentifierList ":=" ExpressionList .

It is a shorthand for a regular variable declaration with initializer expressions but no types:

Answer 2

Keep on going to page 12 of the tour!

A Tour of Go

Short variable declarations

Inside a function, the := short assignment statement can be used in place of a var declaration with implicit type.

(Outside a function, every construct begins with a keyword and the := construct is not available.)

Answer 3

As others have explained already, := is for both declaration, and assignment, whereas = is for assignment only.

For example, var abc int = 20 is the same as abc := 20.

It's useful when you don't want to fill up your code with type or struct declarations.

Answer 4

:= is not an operator. It is a part of the syntax of the Short variable declarations clause.

more on this: https://golang.org/ref/spec#Short_variable_declarations

Answer 5

The := syntax is shorthand for declaring and initializing a variable, example f := "car" is the short form of var f string = "car"

The short variable declaration operator(:=) can only be used for declaring local variables. If you try to declare a global variable using the short declaration operator, you will get an error.

Refer official documentation for more details

Answer 6

According to my book on Go, it is just a short variable declaration statement exactly the same as

var s = ""

But it is more easy to declare, and the scope of it is less expansive. A := var decleration also can't have a type of interface{}. This is something that you will probably run into years later though

Answer 7

:= means that Golang guess which type of variable

example var number uint16 = 260 this is explicit variable declaration

var number = 260 what this means is telling to GOLANG to implicitly define what type this variable should be

number := 260 expression assignment operator same thing like before but without var and tell to GOLANG guess what type this is

Answer 8

:= represents a variable, we can assign a value to a variable using :=.