channel 1

package main

func main() {
	c := make(chan int, 1)
	for done := false; !done; {
		select {
		default:
			print(1)
			done = true
		case <-c:
			print(2)
			c = nil
		case c <- 1:
			print(3)
		}
	}
}

Choices:

• 321
• 21
• 1

Answer: 321

Run it on Go play.

Key points:

• For the 1st loop step, only the operation c <- 1 is non-blocking. So the last case branch is chosen.
• For the 2nd loop step, only the operation <-c is non-blocking. So the first case branch is chosen.
• For the 3rd loop step, both the channel operations are blocking. So the default branch is chosen.

• slice: 1, 2, 3
• map: 1
• channel: 1
• loop: 1, 2, 3, 4
• switch: 1
• defer: 1, 2
• panic/recover: 1, 2
• reflect: 1, 2
• const: 1, 2, 3
• operator: 1, 2, 3
• function call: 1
• scope: 1, 2
• nil: 1
• embedding: 1

(more are coming ...)