Here is a self-contained excerpt:

  type Any = interface{}

  type Enumerator func(yield func(element Any))

  // Select creates an Enumerator which applies f to each of elements.
  func (loop Enumerator) Select(f func(Any) Any) Enumerator {
    return func(yield func(Any)) {
      loop(func(element Any) {
        value := f(element)
        yield(value)
      })
    }
  }

  // Range creates an Enumerator which counts from start
  // up to start + count - 1.
  func Range(start, count int) Enumerator {
    end := start + count
    return func(yield func(Any)) {
      for i := start; i < end; i++ {
        yield(i)
      }
    }
  }

  squares := Range(1, 10).Select(func(x Any) Any { return x.(int) * x.(int) })
  squares(func(num Any) {
    Println(num)
  })
  // Output:
  // 1
  // 4
  // 9
  // 16
  // 25
  // 36
  // 49
  // 64
  // 81
  // 100