def readpartial(size = BUFFER_SIZE)
      return unless @pending_response

      chunk = @parser.read(size)
      return chunk if chunk

      finished = (read_more(size) == :eof) || @parser.finished?
      chunk    = @parser.read(size)
      finish_response if finished

      chunk.to_s
    end
def readpartial(size = BUFFER_SIZE)
      return unless @pending_response

      chunk = @parser.read(size)
      return chunk if chunk

      finished = (read_more(size) == :eof) || @parser.finished?
      chunk    = @parser.read(size)
      finish_response if finished

      chunk.to_s
    end
Read a chunk of the body

 @return [String] data chunk
 @return [nil] when no more data left