code: async function download(remoteFile){
      // strip path
      let localFilename = _path.basename(remoteFile);
  
      // local file with same name already available ?
      if (await _fs.exists(remoteFile)){
          // change filename
          localFilename += '.' + (new Date().getTime());
  
          _logger.log('Local file "' + remoteFile + '" already exist - new file renamed to "' + localFilename + '"');
      }
  
      // try to establish a connection to the module
      await getConnection();
  
      _logger.log('Downloading "' + remoteFile + '" ...');
  
      let data = null;
  
      // download the file
      try{
          data = await _nodeMcuConnector.download(remoteFile);
          _logger.log('Data Transfer complete!');
  
      }catch(e){
          _logger.debug(e);
          throw new Error('Data Transfer FAILED!');
      }
  
      // store the file
      try{
          await _fs.writeFile(localFilename, data);
          _logger.log('File "' + localFilename + '" created');
      }catch(e){
          _logger.debug(e);
          throw new Error('i/o error - cannot save file');
      }
  }
docs: download a remote file from nodemcu