Beautiful Streaming Filter, Map, and Collect using Channel Struct-wrapper

main.go

package main

import (
	"fmt"
	"strconv"
)

type Power struct {
	up int
}

func main() {
	s := []int{2, 3, 5, 7, 11, 13}
	fmt.Println("s ==", s)

	result := filter(s).
		  mapNow().
		  collect()

	fmt.Println(result)
}

func filter(nums []int) Mapper {
	m := Mapper{make(chan int)}

	go func() {
		for _, v := range nums {
			if v > 3 && v < 13 {
				m.channel <- v
			}
		}
		close(m.channel)
	}()

	return m
}

type Mapper struct {
	channel chan int
}

func (m Mapper) mapNow() Collector {
	collector := Collector{make(chan Power)}

	go func() {
		for v := range m.channel {
			collector.channel <- Power{v}
		}
		close(collector.channel)
	}()

	return collector
}

type Collector struct {
	channel chan Power
}

func (c Collector) collect() string {
	powers := "The powers: "
	pow := 0

	for v := range c.channel {
		pow += v.up
	}

	return powers + strconv.Itoa(pow)
}