code: func NewV4() (UUID, error) {
  	u := UUID{}
  	if _, err := randomReader.Read(u[:]); err != nil {
  		return Nil, err
  	}
  	u.setVersion(V4)
  	u.setVariant(VariantRFC4122)
  
  	return u, nil
  }
docs: // NewV4 returns random generated UUID.