What is new in Go 1.21?
In this section, we are going to talk about two new features that came with Go 1.21: The sync.OnceFunc() function of the standard library and the built-in function clear, which deletes or zeroes out all elements of a map, a slice, or a type parameter type.
We are going to begin with the sync.OnceFunc() function.
The sync.OnceFunc() function
The sync.OnceFunc() function is a helper function of the sync package. Its full signature is func OnceFunc(f func()) func(), which means that it accepts a function as a parameter and returns another function. In more detail, sync.OnceFunc() returns a function that invokes function f only once—the important detail here is the only once.
This might look unclear now but the presented code, which is saved as syncOnce.go, is going to shed some light on the use of sync.OnceFunc(). The code of syncOnce.go is presented in two parts. The first part is the following:
package main
import (
"fmt...
