Go functions may be closures. A closure is a function value that references variables from outside its body. The function may access and assign to the referenced variables; in this sense the function is "bound" to the variables.

For example, the adder function returns a closure. Each closure is bound to its own sum variable.

package main 

import "fmt"

func adder() func(int) int {

    sum :=

    return func(x int) int {

        sum += x

        return sum

    }

}

func main() {

    pos, neg := adder(), adder()

    for i := ; i < ; i++ {

        fmt.Println(

            pos(i),

            neg(-*i),

            )

    }

}