feat(tree): add binary tree bfs in golang

codes/go/chapter_tree/binary_tree_bfs.go

@@ -0,0 +1,35 @@
+// File: binary_tree_bfs.go
+// Created Time: 2022-11-26
+// Author: Reanon (793584285@qq.com)
+
+package chapter_tree
+
+import (
+	"container/list"
+	. "github.com/krahets/hello-algo/pkg"
+)
+
+// levelOrder Breadth First Search
+func levelOrder(root *TreeNode) []int {
+	// Let container.list as queue
+	queue := list.New()
+	// 初始化队列，加入根结点
+	queue.PushBack(root)
+	// 初始化一个切片，用于保存遍历序列
+	nums := make([]int, 0)
+	for queue.Len() > 0 {
+		// poll
+		node := queue.Remove(queue.Front()).(*TreeNode)
+		// 保存结点
+		nums = append(nums, node.Val)
+		if node.Left != nil {
+			// 左子结点入队
+			queue.PushBack(node.Left)
+		}
+		if node.Right != nil {
+			// 右子结点入队
+			queue.PushBack(node.Right)
+		}
+	}
+	return nums
+}