Example of Using Fan In design pattern

fanin.go

package main

// Merge function is based from https://github.com/tmrts/go-patterns with little modification

import (
  "sync"
  "fmt"
  "math/rand"
)

func main(){
  size := 20
  massiveChannel := make([]chan int, size)
  for o := 0; o < size; o++ {
    massiveChannel[o] = channelArray(randomArray(size)...)
  }
  count := 0
  for v := range Merge(massiveChannel...) {
    fmt.Printf("%d ", v)
    count++
    if count%size == 0 {
      fmt.Printf("\n")
    }
  }
}
func randomArray(n int) []int {
  var wg sync.WaitGroup
  array := make([]int, n)
  wg.Add(n)
  go func() {
    for i := 0; i < n; i++ {
      array[i] = rand.Intn(10)
      wg.Done()
    }
  }()
  wg.Wait()
  fmt.Println(array)
  return array
}

func channelArray(a ...int) chan int {
  var wg sync.WaitGroup
  channel := make(chan int, len(a))
  wg.Add(len(a))
  go func() {
    for _, number := range a {
      channel <- number
      wg.Done()
    }
  }()
  wg.Wait()
  defer close(channel)
  return channel
}

func Merge(cs ...chan int) <-chan int {
  var wg sync.WaitGroup

  out := make(chan int, 1)

  send := func(c <-chan int) {
    for n := range c {
      out <- n
    }
    wg.Done()
  }

  wg.Add(len(cs))
  for _, c := range cs {
    go send(c)
  }

  go func() {
    wg.Wait()
    close(out)
  }()
  return out
}