event: add some documentation

event/event.go

@@ -7,8 +7,16 @@ import (
 	"sync"
 )
 
+// Subscription is implemented by event subscriptions.
 type Subscription interface {
+	// Chan returns a channel that carries events.
+	// Implementations should return the same channel
+	// for any subsequent calls to Chan.
 	Chan() <-chan interface{}
+
+	// Unsubscribe stops delivery of events to a subscription.
+	// The event channel is closed.
+	// Unsubscribe can be called more than once.
 	Unsubscribe()
 }
 
@@ -21,6 +29,7 @@ type TypeMux struct {
 	stopped bool
 }
 
+// ErrMuxClosed is returned when Posting on a closed TypeMux.
 var ErrMuxClosed = errors.New("event: mux closed")
 
 // NewTypeMux creates a running mux.

event/example_test.go

+package event
+
+import "fmt"
+
+func ExampleTypeMux() {
+	type someEvent struct{ I int }
+	type otherEvent struct{ S string }
+	type yetAnotherEvent struct{ X, Y int }
+
+	var mux TypeMux
+
+	// Start a subscriber.
+	done := make(chan struct{})
+	sub := mux.Subscribe(someEvent{}, otherEvent{})
+	go func() {
+		for event := range sub.Chan() {
+			fmt.Printf("Received: %#v\n", event)
+		}
+		fmt.Println("done")
+		close(done)
+	}()
+
+	// Post some events.
+	mux.Post(someEvent{5})
+	mux.Post(yetAnotherEvent{X: 3, Y: 4})
+	mux.Post(someEvent{6})
+	mux.Post(otherEvent{"whoa"})
+
+	// Stop closes all subscription channels.
+	// The subscriber goroutine will print "done"
+	// and exit.
+	mux.Stop()
+
+	// Wait for subscriber to return.
+	<-done
+
+	// Output:
+	// Received: event.someEvent{I:5}
+	// Received: event.someEvent{I:6}
+	// Received: event.otherEvent{S:"whoa"}
+	// done
+}