first

course/13-channels/exercises/9a-channel_quiz/multiple_choice.json

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+{
+  "question": "What happens when you send to a closed channel?",
+  "answers": [
+    "Panic",
+    "The sender will block forever",
+    "The receiver will block forever"
+  ]
+}

course/13-channels/exercises/9a-channel_quiz/readme.md

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+# Channels Review
+
+Here are a few extra things you should understand about channels from [Dave Cheney's awesome article](https://dave.cheney.net/2014/03/19/channel-axioms).
+
+## A send to a nil channel blocks forever
+
+```go
+var c chan string // c is nil
+c <- "let's get started" // blocks
+```
+
+## A receive from a nil channel blocks forever
+
+```go
+var c chan string // c is nil
+fmt.Println(<-c) // blocks
+```
+
+## A send to a closed channel panics
+
+```go
+var c = make(chan int, 100)
+close(c)
+c <- 1 // panic: send on closed channel
+```
+
+## A receive from a closed channel returns the zero value immediately
+
+```go
+var c = make(chan int, 100)
+close(c)
+fmt.Println(<-c) // 0
+```