const 2

package main

const X = 3

func main() {
	const (
		X = X + X
		Y
	)
	
	println(X, Y)
}

• Go spec says: Within a parenthesized const declaration list the expression list may be omitted from any but the first ConstSpec. Such an empty list is equivalent to the textual substitution of the first preceding non-empty expression list and its type if any.
• a local identifier will shadow the global identifier with the same name.

	const (
		X = X + X // here the two "X" are both the global one
		Y = X + X // here the two "X" are both the local one
	)

package main

func main() {
	const (
		iota = iota
		X
		Y
	)
	println(X, Y)
}