You're on assignment part 2/2 for this lesson.
Here are a few extra things you should understand about channels from Dave Cheney's awesome article.
var s []int // s is nil
var c chan string // c is nil
var s = make([]int, 5) // s is initialized and not nil
var c = make(chan int) // c is initialized and not nil
var c chan string // c is nil
c <- "let's get started" // blocks
var c chan string // c is nil
fmt.Println(<-c) // blocks
var c = make(chan int, 100)
close(c)
c <- 1 // panic: send on closed channel
var c = make(chan int, 100)
close(c)
fmt.Println(<-c) // 0