Blank identifier

The blank identifier is represented by the underscore character _. It serves as an anonymous placeholder instead of a regular (non-blank) identifier and has special meaning in declarations, as an operand, and in assignment statements.

Ah, the blank identifier!

We’ve talked about it in a few contexts already. Namely, struct field names, as well as binding variables. But it can be used in many places… Including a few surprising places, where it never serves a purpose. This is not at all an exhaustive list, more a reminder of what the blank identifier does.

func() {
	_: // A blank label does nothing. Has no scope, cannot be referenced...

	var _ = 1           // This blank variable isn't very useful
	_, err := doThing() // But this one discards a return value from a function

	for _, x := range things { // This blank identifier discards the range index
		/* ... */
	}

  x, _ := someInterface.(int) // Prevent the type assertion from panicking
}

Quotes from The Go Programming Language Specification Version of December 15, 2022