erlang httpc 上传文件

-define(URL, "http://127.0.0.1:1000/").
-define(CRLF, "\r\n").


demo_upload_file() ->
    FileName = "/home/dash/avatar.png",
    {ok,Binary} = file:read_file(FileName),
    FieldName = "avatar",
    
    BinAccessToken = list_to_binary(AccessToken),
    BinFileName = list_to_binary(FileName),
        BinFieldName = list_to_binary(FieldName),
   
    Boundary = <<"upload_boundary">>,
    Body = <<"--", Boundary/binary, ?CRLF,
            "Content-Disposition: form-data; name=\"access_token\"", ?CRLF,
            ?CRLF,
            BinAccessToken/binary, ?CRLF,

        　　"--", Boundary/binary, ?CRLF,
            "Content-Disposition: form-data; name=\"", BinFieldName/binary,
            "\"; filename=\"", BinFileName/binary, "\"", ?CRLF,
            "Content-Type: application/octet-stream", ?CRLF,
            ?CRLF,
            Binary/binary, ?CRLF,
            "--", Boundary/binary, "--", ?CRLF,
            ?CRLF>>,
    ContentType = "multipart/form-data;boundary=upload_boundary",
    
    case httpc:request(post, {?Url, [], ContentType, Body}, [], []) of
        {ok, {_, _, Response}} ->
          Response;
        _ ->
            error
    end.