code: func (id ULID) MarshalBinaryTo(dst []byte) error {
  	if len(dst) != len(id) {
  		return ErrBufferSize
  	}
  
  	copy(dst, id[:])
  	return nil
  }
docs: // MarshalBinaryTo writes the binary encoding of the ULID to the given buffer.
  // ErrBufferSize is returned when the len(dst) != 16.