Challenge 1 — Solution

Task: Write a function cube(n int, results chan int) that sends n³
into results. In main, create an unbuffered channel, launch
cube(4, results) as a goroutine, receive the value, and print it.

package main

import "fmt"

func cube(n int, results chan int) {
	results <- n * n * n
}

func main() {
	results := make(chan int)

	go cube(4, results)

	value := <-results
	fmt.Println(value)
}


Expected output:

64

Notes:
- results := make(chan int) creates an UNBUFFERED channel — sending
  into it blocks until something is ready to receive, and vice
  versa.
- value := <-results blocks main() until cube's goroutine actually
  sends a value, which is exactly why no time.Sleep workaround is
  needed here — the channel itself provides the synchronization.
- cube runs as a separate goroutine, but because main immediately
  tries to receive from results, the two effectively hand off the
  value to each other the moment it's ready.