code: func (r *Reader) ReadFloat64() float64 {
  	if r.err != nil {
  		return 0
  	}
  	var n int
  	n, r.err = io.ReadFull(r.rd, r.b[:8])
  	r.cnt += n
  	if r.err != nil {
  		return 0
  	}
  	bits := binary.LittleEndian.Uint64(r.b[:8])
  	return math.Float64frombits(bits)
  }
docs: // ReadFloat64 reads and returns a float64.