Go concurrency basic example

square.go

package main

import "fmt" 

// Take a variadic list of integers, and launch a goroutine which will block trying to send them on channel 'out'
// Return this channel as a receive-only channel
func gen(ns ...int) <-chan int {
  out := make(chan int) // Create a bidirectional channel
  go func() {
    for _, n := range ns {
      out <- n
    }
    close(out)
  }()
  return out // Demoted to unidirectional receive-only
}

// Create a channel and write the square of the incoming channel elements to it. The incoming receive-only channel is read
// by a launched goroutine, which also writes to the output channel. Let the go routine block waiting for input
// and return the output channel (for consumption by the caller)
func sq(in <-chan int) <-chan int {
  out := make(chan int) // Create a bidirection channel
  go func() {
    for n := range in {   // Note: You don't do for _, n because it's not a slice
      out <- n * n
    }
    close(out)
  }()
  return out
}

// Set up the pipelines
func main() {
  for n := range sq(gen(2,3)) {
    fmt.Println(n)
  }
}