Go - Closures

A closure is a function that references variables defined outside of its own scope:

• The closure is created using an anonymous function defined within another function
• The anonymous function can access and assign to variables from the parent function, even after the parent function has returned
• The anonymous function is returned from the parent function

// A function that returns a closure.
func adder() func(int) int {
  sum := 0

  // Return an anonymous function.
  return func(x int) int {
    // Access a variable from the parent function's scope.
    sum += x
    return sum
  }
}

// Assign the anonymous function to a variable.
f := adder()

f(1) // 1
f(1) // 2
f(1) // 3