Flutter – How to achieve File upload for web and mobile?

I am trying to achieve a simple file upload feature in my flutter app. I need to have it for both web and mobile.

            ///
        class FileUploadController extends GetxController {
          Rx<File?> file = Rx<File?>(null);
          String fileName = '';
          var token =
              'something';

          void pickFile() async {
            try {
              FilePickerResult? result = await FilePicker.platform.pickFiles(
                //type: FileType.image,
                allowMultiple: false,
              );

              if (result != null) {
                if (kIsWeb) {
                  Uint8List? fileBytes = result.files.first.bytes;
                  fileName = result.files.first.name;
                  var objFile = await createFileFromBytes(fileBytes);
                  file.value = objFile;
                } //
                else {
                  file.value = File(result.files.single.path!);
                }
              }
            } //
            catch (e) {
              print(e);
            }
          }

          Future<File> createFileFromBytes(Uint8List? bytes) async {
            var cleanString = '';
            var lstBytes = bytes!.toList();
            // Decode the bytes as a UTF-8 string
            String decodedCode = utf8.decode(lstBytes, allowMalformed: true);
            if (decodedCode.contains('�')) {
              cleanString = decodedCode.replaceAll('�', '');
            }

            // Create a File object from the decoded string
            var file = File.fromRawPath(Uint8List.fromList(cleanString.codeUnits));
            return file;
          }

          void uploadFile() async {
            try {
              if (file.value == null) {
                return;
              }

              // Set API endpoint URL
              Uri uri =
                  Uri.parse('xxxx');

              // Create multipart request
              var request = http.MultipartRequest('POST', uri);

              request.fields.addAll({
                "facility_id": "380",
                "module_id": "1",
                "id": "3263",
              });

              // Add file to request
              String fieldName = 'files';
              fileName = kIsWeb ? fileName : file.value!.path.split('/').last;
              var checkFile = file.value;
    //// getting error here: Un
              var bytesData = await file.value!.readAsBytes();
              request.files.add(http.MultipartFile.fromBytes(
                fieldName,
                bytesData,
                filename: fileName,
              ));

              // Set headers
              request.headers.addAll({
                "Authorization": "Bearer $token",
                "Content-Type": "multipart/form-data",
                "Content-Length": file.value!.lengthSync().toString(),
                "Accept": "*/*",
              });

              // Send request
              var response = await request.send();

              // Check response status code
              if (response.statusCode == 200) {
                print('File uploaded successfully!');
              } else {
                print('Error uploading file.');
              }
            } //
            catch (e) {
              print(e);
            }
          }

          ///
        }

Error: Unsupported Operation _Namespace