This example illustrates pipelines in Go. There are two channels. The first channel (channel A) is used for getting the random numbers from the first function and sending them to the second function. The second channel (channel B) is used by the second function for sending the acceptable random numbers to the third function. The third function i…

pipeline.go

package main

import (
	"fmt"
	"math/rand"
	"os"
	"strconv"
	"time"
)

var closeA = false

var data = make(map[int]bool)

func random(min, max int) int {
	return rand.Intn(max-min) + min
}

func first(min, max int, out chan<- int) {
	for {
		if closeA {
			close(out)
			return
		}
		out <- random(min, max)
		time.Sleep(1 * time.Second)
	}
}

func second(out chan<- int, in <-chan int) {
	for x := range in {
		fmt.Print(x, " ")
		_, ok := data[x]
		if ok {
			closeA = true
		} else {
			data[x] = true
			out <- x
		}
	}
	fmt.Println()
	close(out)
}

func third(in <-chan int) {
	var sum int
	for x := range in {
		sum += x
	}
	fmt.Printf("The sum of the random numbers is %d\n", sum)
}

func main() {
	if len(os.Args) != 3 {
		fmt.Println("Need two integer parameters!")
		os.Exit(1)
	}

	n1, _ := strconv.Atoi(os.Args[1])
	n2, _ := strconv.Atoi(os.Args[2])

	if n1 > n2 {
		fmt.Printf("%d should be smaller than %d\n", n1, n2)
		return
	}
	rand.Seed(time.Now().UnixNano())
	A := make(chan int)
	B := make(chan int)

	go first(n1, n2, A)
	go second(B, A)
	third(B)
}

/*
Input:
> go run pipeline.go 1 100

Output: 
55 77 17 68 8 84 39 44 10 92 19 65 69 64 55       
The sum of the random numbers is 711
*/