Method on_int64

example/validate.cpp:50–50

        bool on_string( string_view, std::size_t, boost::system::error_code& ) { return true; }
        bool on_number_part( string_view, boost::system::error_code& ) { return true; }
        bool on_int64( std::int64_t, string_view, boost::system::error_code& ) { return true; }
        bool on_uint64( std::uint64_t, string_view, boost::system::error_code& ) { return true; }
        bool on_double( double, string_view, boost::system::error_code& ) { return true; }
        bool on_bool( bool, boost::system::error_code& ) { return true; }