fix(netxlite/quic): wrap Close (#509)

While there, make sure netxlite has 100% coverage.

Part of https://github.com/ooni/probe/issues/1733 and diff
has been extracted from https://github.com/ooni/probe-cli/pull/506.

internal/netxlite/http_test.go

@@ -75,7 +75,12 @@ func TestHTTPTransportLogger(t *testing.T) {
 				},
 			}
 			client := &http.Client{Transport: txp}
-			resp, err := client.Get("https://www.google.com")
+			req, err := http.NewRequest("GET", "https://www.google.com", nil)
+			if err != nil {
+				t.Fatal(err)
+			}
+			req.Header.Set("User-Agent", "miniooni/0.1.0-dev")
+			resp, err := client.Do(req)
 			if err != nil {
 				t.Fatal(err)
 			}

internal/netxlite/quic.go

@@ -394,6 +394,16 @@ func (c *quicErrWrapperUDPLikeConn) ReadFrom(b []byte) (int, net.Addr, error) {
 	return n, addr, nil
 }
 
+// Close implements quicx.UDPLikeConn.Close.
+func (c *quicErrWrapperUDPLikeConn) Close() error {
+	err := c.UDPLikeConn.Close()
+	if err != nil {
+		return errorsx.NewErrWrapper(
+			errorsx.ClassifyGenericError, errorsx.ReadFromOperation, err)
+	}
+	return nil
+}
+
 // quicDialerErrWrapper is a dialer that performs quic err wrapping
 type quicDialerErrWrapper struct {
 	QUICDialer

internal/netxlite/quic_test.go

@@ -472,6 +472,7 @@ func TestQUICLoggerDialer(t *testing.T) {
 func TestNewSingleUseQUICDialer(t *testing.T) {
 	sess := &mocks.QUICEarlySession{}
 	qd := NewSingleUseQUICDialer(sess)
+	defer qd.CloseIdleConnections()
 	outsess, err := qd.DialContext(
 		context.Background(), "", "", &tls.Config{}, &quic.Config{})
 	if err != nil {
@@ -618,6 +619,37 @@ func TestQUICErrWrapperUDPLikeConn(t *testing.T) {
 			}
 		})
 	})
+
+	t.Run("Close", func(t *testing.T) {
+		t.Run("on success", func(t *testing.T) {
+			conn := &quicErrWrapperUDPLikeConn{
+				UDPLikeConn: &mocks.QUICUDPLikeConn{
+					MockClose: func() error {
+						return nil
+					},
+				},
+			}
+			err := conn.Close()
+			if err != nil {
+				t.Fatal(err)
+			}
+		})
+
+		t.Run("on failure", func(t *testing.T) {
+			expectedErr := io.EOF
+			conn := &quicErrWrapperUDPLikeConn{
+				UDPLikeConn: &mocks.QUICUDPLikeConn{
+					MockClose: func() error {
+						return expectedErr
+					},
+				},
+			}
+			err := conn.Close()
+			if err == nil || err.Error() != errorsx.FailureEOFError {
+				t.Fatal("unexpected err", err)
+			}
+		})
+	})
 }
 
 func TestQUICDialerErrWrapper(t *testing.T) {