code: async function gunzip(input, dst){
      // is input a filename or stream ?
      if (typeof input === 'string'){
          input = await _fileInputStream(input);
      }
  
      // decompress
      const gzipStream = input.pipe(_zlib.createGunzip());
  
      // write content to file
      return _fileOutputStream(gzipStream, dst);
  }
docs: decompress a file