code: func New(store *store.MemoryStore, config *Config) *KeyManager {
  	for _, subsys := range config.Subsystems {
  		if subsys != SubsystemGossip && subsys != SubsystemIPSec {
  			return nil
  		}
  	}
  	return &KeyManager{
  		config:  config,
  		store:   store,
  		keyRing: &keyRing{lClock: genSkew()},
  	}
  }
docs: // New creates an instance of keymanager with the given config