Add code source blocks to the chapter Graph.

Fix "函数" and "方法"

codes/go/chapter_graph/graph_adjacency_list.go

@@ -15,6 +15,7 @@ type vertex struct {
 	val int
 }
 
+/* 构造方法 */
 func newVertex(val int) vertex {
 	return vertex{
 		val: val,
@@ -28,7 +29,7 @@ type graphAdjList struct {
 	adjList map[vertex]map[vertex]struct{}
 }
 
-/* 构造函数 */
+/* 构造方法 */
 func newGraphAdjList(edges [][]vertex) *graphAdjList {
 	g := &graphAdjList{
 		adjList: make(map[vertex]map[vertex]struct{}),

codes/go/chapter_graph/graph_adjacency_matrix.go

@@ -14,6 +14,7 @@ type graphAdjMat struct {
 	adjMat [][]int
 }
 
+/* 构造方法 */
 func newGraphAdjMat(vertices []int, edges [][]int) *graphAdjMat {
 	// 添加顶点
 	n := len(vertices)