code: func (m *resolversMap) LoadOrStore(key string, value resolver.Resolver) (resolver.Resolver, bool) {
  	i, _ := m.data.LoadOrStore(key, value)
  	s, ok := i.(resolver.Resolver)
  	return s, ok
  }
docs: // LoadOrStore will return an existing key or
  // store the value if not already in the map