adding simpler channels koans as prelude to concurrency

about_channels.go

@@ -0,0 +1,27 @@
+package go_koans
+
+func aboutChannels() {
+  ch := make(chan string, 2)
+
+  assert(len(ch) == __int__) // channels are like buffers
+
+  ch<- "foo" // i mean, "metaphors are like similes"
+
+  assert(len(ch) == __int__) // they can be queried for queued items
+
+  assert(<-ch == __string__) // items can be popped out of them
+
+  assert(len(ch) == __int__) // and len() always reflects the "current" queue status
+
+  // the 'go' keyword runs a function-call in a new "goroutine"
+  // which executes "concurrently" with the calling "goroutine"
+  go func() {
+    // your code goes here
+  }()
+
+  assert(__delete_me__) // we'll need to make room for the queue, or suffer deadlocks
+
+  ch<- "bar" // this send will succeed
+  ch<- "quux" // there's enough room for this send too
+  ch<- "extra" // but the buffer only has two slots
+}

setup_koans_test.go

@@ -33,6 +33,7 @@ func TestKoans(t *testing.T) {
   aboutPointers()
   aboutStructs()
   aboutAllocation()
+  aboutChannels()
   aboutConcurrency()
   aboutPanics()