code: func Unregister(name string) *Scheme {
  	scheme, ok := schemeMap[name]
  	if ok {
  		for _, alias := range scheme.Aliases {
  			delete(schemeMap, alias)
  		}
  		delete(schemeMap, name)
  		return scheme
  	}
  	return nil
  }
docs: // Unregister unregisters a Scheme and all associated aliases.