fix length calculcation for CONNECTION_CLOSE frames

internal/wire/connection_close_frame.go

@@ -62,7 +62,7 @@ func parseConnectionCloseFrame(r *bytes.Reader, version protocol.VersionNumber)
 func (f *ConnectionCloseFrame) Length(version protocol.VersionNumber) protocol.ByteCount {
 	length := 1 + utils.VarIntLen(uint64(f.ErrorCode)) + utils.VarIntLen(uint64(len(f.ReasonPhrase))) + protocol.ByteCount(len(f.ReasonPhrase))
 	if !f.IsApplicationError {
-		length++ // for the frame type
+		length += utils.VarIntLen(f.FrameType) // for the frame type
 	}
 	return length
 }

internal/wire/connection_close_frame_test.go

@@ -132,6 +132,7 @@ var _ = Describe("CONNECTION_CLOSE Frame", func() {
 			b := &bytes.Buffer{}
 			f := &ConnectionCloseFrame{
 				ErrorCode:    0xcafe,
+				FrameType:    0xdeadbeef,
 				ReasonPhrase: "foobar",
 			}
 			Expect(f.Write(b, versionIETFFrames)).To(Succeed())