code: func (m *Manager) Get(id string) (*User, error) {
  	var user User
  
  	objectID := bson.ObjectIdHex(id)
  
  	if err := m.getUserCollection().FindId(objectID).One(&user); err != nil {
  		return nil, err
  	}
  
  	return &user, nil
  }
docs: // Get user by ID.