Constants

Declaration: const name type = expression

const greeting string = "Hello World"

Untyped Constants

Constants can be untyped which is useful for numbers.
The constant will be implicitly converted to the required type.

Examples from package math:

const (
    E        = 2.71828182845904523536028747135266249775724709369995957496696763
    Pi       = 3.14159265358979323846264338327950288419716939937510582097494459
    MaxInt8  = 1<<7 - 1 // 127
    MinInt32 = -1 << 31 // -2147483648
)

Enums

Go has no enumerations but they can be mimicked by using constants.
The value for the keyword iota is incremented by one after each line.

const (
    Summer int = iota // 0
    Autumn            // 1
    Winter            // 2
    Spring            // 3
)

type Direction int

const (
    North Direction = iota // 0
    East                   // 1
    South                  // 2
    West                   // 3
)