once

Documentation

Overview

This package provides a single function, Do, to run a function exactly once, usually used as part of initialization.

Index

• func Do(f func())

Functions

func Do

func Do(f func())

Do is the the only exported piece of the package. For one-time initialization that is not done during init, wrap the initialization in a niladic function f() and call

Do(f)

If multiple processes call Do(f) simultaneously with the same f argument, only one will call f, and the others will block until f finishes running.

Since a func() expression typically evaluates to a differerent function value each time it is evaluated, it is incorrect to pass such values to Do. For example,

func f(x int) {
	Do(func() { fmt.Println(x) })
}

behaves the same as

func f(x int) {
	fmt.Println(x)
}

because the func() expression in the first creates a new func each time f runs, and each of those funcs is run once.