net/http/httptest: close res.Body in test

Signed-off-by: guoguangwu <guoguangwug@gmail.com>

src/net/http/httptest/server_test.go

@@ -83,6 +83,7 @@ func testGetAfterClose(t *testing.T, newServer newServerFunc) {
 		t.Fatal(err)
 	}
 	got, err := io.ReadAll(res.Body)
+	res.Body.Close()
 	if err != nil {
 		t.Fatal(err)
 	}