Go: What is the difference between var and := in Go?

var — explicit declaration. := — short variable declaration.

var:

• Can declare anywhere.
• Can specify type.
• Can declare without initializing.

1// Package level
2var x int
3
4// Function level
5var y int = 42
6var z = 42  // Type inferred
7
8// Multiple
9var a, b, c int

:= (short declaration):

• Only inside functions.
• Type inferred.
• Must initialize.
• At least one new variable.

1func main() {
2    x := 42  // Type inferred as int
3    y, z := 1, 2  // Multiple
4}

Key differences:

• var — package scope, no initialization needed.
• := — function scope only, must initialize.