What Is iota in Go and How to Use It for Enums

iota is a predeclared constant in Go that automatically increments by 1 for each line in a const block, starting at 0. It is primarily used to create compact, readable enumerations without manually typing sequential numbers.

const (
	FormatUnknown Format = iota
	FormatV7
	FormatUSTAR
	FormatPAX
	FormatGNU
)

This pattern assigns 0 to FormatUnknown, 1 to FormatV7, 2 to FormatUSTAR, and so on, ensuring values remain unique and sequential.

iota is a built-in counter that Go uses to assign numbers to a list of constants automatically. Instead of typing 0, 1, 2, 3 yourself, you just list your names, and Go fills in the numbers for you. It works like a numbered list in a document where the numbers update themselves if you add or remove items.