Challenge 2 — Solution

Task: Given numbers := []int{1, 2, 3, 4, 5}, launch a goroutine per
number that sends its square into a buffered channel sized to
len(numbers). Receive all 5 results in a loop, summing them into a
total printed at the end.

package main

import "fmt"

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

func main() {
	numbers := []int{1, 2, 3, 4, 5}
	results := make(chan int, len(numbers))

	for _, n := range numbers {
		go square(n, results)
	}

	total := 0
	for i := 0; i < len(numbers); i++ {
		total += <-results
	}

	fmt.Println("Total:", total)
}


Expected output:

Total: 55

Notes:
- The buffered channel (capacity 5) lets all 5 goroutines send their
  results without any of them having to wait for a receiver to be
  ready first.
- The receiving loop runs exactly len(numbers) times, guaranteeing
  every result is collected — the ORDER they arrive in is not
  guaranteed, but the total (1+4+9+16+25 = 55) is the same regardless
  of order, since addition doesn't care about sequence.
- total += <-results both receives a value from the channel and adds
  it to total in one expression.