Use of defer in Go

Question

What is the use of defer in Go? The language documentation says it is executed when the surrounding function returns. Why not just put the code at end of given

Answer 1

A defer statement defers the execution of a function until the surrounding function returns.

This example demonstrates defer functionality:

func elapsed(what string) func() {
    start := time.Now()
    fmt.Println("start")
    return func() {
        fmt.Printf("%s took %v\n", what, time.Since(start))
    }
}

func main() {
    defer elapsed("page")()
    time.Sleep(time.Second * 3)
}

Out:

start
page took 3s