code: func (w *Writer) WriteFloat64(f float64) {
  	if w.err != nil {
  		return
  	}
  	bits := math.Float64bits(f)
  	binary.LittleEndian.PutUint64(w.b[:8], bits)
  	w.wr.Write(w.b[:8])
  }
docs: // WriteFloat64 writes a float64.