code: func (tableNode *routingTableNode) SetChild(index int, c *routingTableNode) {
  	tableNode.Lock()
  	defer tableNode.Unlock()
  
  	tableNode.children[index] = c
  }
docs: // SetChild sets routingTableNode's left or right child. When index is 0, it's
  // the left child, if 1, it's the right child.