Add public session CloseChan method (#44)

session.go

@@ -123,6 +123,12 @@ func (s *Session) IsClosed() bool {
 	}
 }
 
+// CloseChan returns a read-only channel which is closed as
+// soon as the session is closed.
+func (s *Session) CloseChan() <-chan struct{} {
+	return s.shutdownCh
+}
+
 // NumStreams returns the number of currently open streams
 func (s *Session) NumStreams() int {
 	s.streamLock.Lock()

session_test.go

@@ -619,7 +619,7 @@ func TestHalfClose(t *testing.T) {
 	if err != nil {
 		t.Fatalf("err: %v", err)
 	}
-	if _, err := stream.Write([]byte("a")); err != nil {
+	if _, err = stream.Write([]byte("a")); err != nil {
 		t.Fatalf("err: %v", err)
 	}
 
@@ -639,7 +639,7 @@ func TestHalfClose(t *testing.T) {
 	}
 
 	// Send more
-	if _, err := stream.Write([]byte("bcd")); err != nil {
+	if _, err = stream.Write([]byte("bcd")); err != nil {
 		t.Fatalf("err: %v", err)
 	}
 	stream.Close()

stream.go

@@ -188,7 +188,7 @@ START:
 
 	// Send the header
 	s.sendHdr.encode(typeData, flags, s.id, max)
-	if err := s.session.waitForSendErr(s.sendHdr, body, s.sendErr); err != nil {
+	if err = s.session.waitForSendErr(s.sendHdr, body, s.sendErr); err != nil {
 		return 0, err
 	}