package main

import (
    "fmt"
    "sync"
    "time"
)

type job func(out chan interface{})

var executePipeline = func(jobs ...job) chan interface{} {
    out := make(chan interface{})
    wg := &sync.WaitGroup{}
    for _, j := range jobs {
        wg.Add(1)
        go func(j job) {
            j(out)
            wg.Done()
        }(j)
    }
    go func() {
        wg.Wait()
        close(out)
    }()
    return out
}

func main() {
    start := time.Now()

    rr := executePipeline(func(out chan interface{}) {
        time.Sleep(time.Millisecond * 100)
        out <- "1"
    }, func(out chan interface{}) {
        time.Sleep(time.Millisecond * 200)
        out <- "2"
    }, func(out chan interface{}) {
        time.Sleep(time.Millisecond * 300)
        out <- "3"
    }, func(out chan interface{}) {
        time.Sleep(time.Millisecond * 400)
        out <- "4"
    })

    for r := range rr {
        fmt.Println(r.(string))
    }

    fmt.Printf("time since start: %v \n", time.Since(start))
}