code: func (registry *Registry) Register(name string, check Checker) {
  	if registry == nil {
  		registry = DefaultRegistry
  	}
  	registry.mu.Lock()
  	defer registry.mu.Unlock()
  	_, ok := registry.registeredChecks[name]
  	if ok {
  		panic("Check already exists: " + name)
  	}
  	registry.registeredChecks[name] = check
  }
docs: // Register associates the checker with the provided name.