Variable Declarations

// declare variable name of foo with int type
var foo int

// assign only
foo = 10

// declare variable and assign
var foo int
foo = 10

var foo int = 10

// implicit
var foo = 32

// shorthand for declare and assign
foo := 10

Variable Scoping

Short Variable Declaration

You cannot use short variable declaration outside a function

// illegal
package main

n := 1

func main() {}

// legal
package main

var n = 1

func main() {}

Semicolon (;)

// semicolon syntax
if err := failFunction(); err != nil {
  log.Fatal(err)
}

// can be rewritten as block scope
{
  err := failFunction()
  if err != nil {
      log.Fatal(err)
  }
}

The outer {} brackets act as a block which creates a new scope.

When err is defined before the block scope, a new variable named err will be created inside the new scope will override the value of previously defined err until the end of block scope.

Constants

Cannot be declared using the := syntax

const ConstantValue = "cannot change"

const (
  imageWidth = 160
  jpegQuality = 50
)