AMQP single send - error monad vs nested case

amqp-single-send.erl

-spec send(method(), #amqp_params_direct{}) -> error_m(ok, term()).
%% @private
send(Method, Params) ->
    do([error_m ||
           Conn <- amqp_connection:start(Params),
           Chan <- amqp_connection:open_channel(Conn),
           return(amqp_channel:call(Chan, Method)),
           return(amqp_channel:close(Chan)),
           amqp_connection:close(Conn)]).

-spec send(method(), #amqp_params_direct{}) -> ok.
%% @private
send(Method, Params) ->
    {Conn, Chan} =
        case amqp_connection:start(Params) of
            {ok, Conn} ->
                case amqp_connection:open_channel(Conn) of
                    {ok, Chan} ->
                        amqp_channel:call(Chan, Method),
                        {Conn, Chan};
                    Error ->
                        {Conn, none}
                end;
            Error ->
                {none, none}
        end,
    case Chan of
        none -> ok;
        _    -> amqp_channel:close(Chan)
    end,
    case Conn of
        none -> ok;
        _    -> amqp_connection:close(Conn)
    end.