code: func (g *SimpleGraph) Adj(v interface{}) ([]interface{}, error) {
  	g.mutex.RLock()
  	defer g.mutex.RUnlock()
  
  	deg, err := g.Degree(v)
  	if err != nil {
  		return nil, ErrVertexNotFound
  	}
  
  	adj := make([]interface{}, deg)
  	i := 0
  	for key := range g.adjacencyList[v] {
  		adj[i] = key
  		i++
  	}
  	return adj, nil
  }
docs: // Adj returns the list of all vertices connected to v