code: func (br *bufReader) Next(n int) []byte {
  	if br.err != nil {
  		return nil
  	}
  	var b []byte
  	b, br.err = br.next(n)
  	return b
  }
docs: // Next returns a slice containing the next n bytes from the buffer,
  // advancing the buffer as if the bytes had been returned by Read.
  // If there are fewer than n bytes in the buffer, Next returns the entire buffer.
  // The slice is only valid until the next call to a read or write method.