code: func Register(name string, factory ValidatorFactory) {
  	typesMu.Lock()
  	defer typesMu.Unlock()
  	if factory == nil {
  		panic("authmethod: Register factory is nil for type " + name)
  	}
  	if _, dup := types[name]; dup {
  		panic("authmethod: Register called twice for type " + name)
  	}
  	types[name] = factory
  }
docs: // Register makes an auth method with the given type available for use. If
  // Register is called twice with the same name or if validator is nil, it
  // panics.