By Golang

// Package graph creates a ItemGraph data structure for the Item type
package graph

import (
    "fmt"
    "sync"
)

// Item the type of the binary search tree
type Item interface{}

// Node a single node that composes the tree
type Node struct {
    value Item
}

func (n *Node) String() string {
    return fmt.Sprintf("%v", n.value)
}

// ItemGraph the Items graph
type ItemGraph struct {
    nodes []*Node
    edges map[Node][]*Node
    lock  sync.RWMutex
}

// AddNode adds a node to the graph
func (g *ItemGraph) AddNode(n *Node) {
    g.lock.Lock()
    g.nodes = append(g.nodes, n)
    g.lock.Unlock()
}

// AddEdge adds an edge to the graph
func (g *ItemGraph) AddEdge(n1, n2 *Node) {
    g.lock.Lock()
    if g.edges == nil {
        g.edges = make(map[Node][]*Node)
    }
    g.edges[*n1] = append(g.edges[*n1], n2)
    g.edges[*n2] = append(g.edges[*n2], n1)
    g.lock.Unlock()
}

// AddEdge adds an edge to the graph
func (g *ItemGraph) String() {
    g.lock.RLock()
    s := ""
    for i := 0; i < len(g.nodes); i++ {
        s += g.nodes[i].String() + " -> "
        near := g.edges[*g.nodes[i]]
        for j := 0; j < len(near); j++ {
            s += near[j].String() + " "
        }
        s += "\n"
    }
    fmt.Println(s)
    g.lock.RUnlock()
}

// Traverse implements the BFS traversing algorithm
func (g *ItemGraph) Traverse(f func(*Node)) {
    g.lock.RLock()
    q := NodeQueue{}
    q.New()
    n := g.nodes[0]
    q.Enqueue(*n)
    visited := make(map[*Node]bool)
    for {
        if q.IsEmpty() {
            break
        }
        node := q.Dequeue()
        visited[node] = true
        near := g.edges[*node]

        for i := 0; i < len(near); i++ {
            j := near[i]
            if !visited[j] {
                q.Enqueue(*j)
                visited[j] = true
            }
        }
        if f != nil {
            f(node)
        }
    }
    g.lock.RUnlock()
}