code: func (r *registry) initAuthPlugin(p *plugin.Plugin) {
  	constructorSymbol, err := p.Lookup(authPluginFactory)
  	if err != nil {
  		panicWithLookupError(authPluginFactory, err)
  	}
  	constructor, ok := constructorSymbol.(func() auth.Filter)
  	if !ok {
  		panicWithDefinitionError(authPluginFactory)
  	}
  
  	filter := constructor()
  	if filter != nil {
  		r.filters = append(r.filters, filter)
  	}
  }
docs: // initAuthPlugin constructs an auth filter from the given plugin