输出格式要求：标题：Go 模板中安全地允许特定 HTML 标签

package main

import (
    "fmt"
    "strings"

    "github.com/jaytaylor/html2text"
    "golang.org/x/net/html"
)

// allowedTags 定义允许的 HTML 标签
var allowedTags = map[string]bool{
    "p":  true,
    "br": true,
    "b":  true,
    "i":  true,
    "a":  true,
}

// allowedAttributes 定义允许的 HTML 属性，以及允许的标签
var allowedAttributes = map[string]map[string]bool{
    "a": {"href": true},
}

// sanitizeHTML 对 HTML 进行清理，只保留白名单中的标签和属性
func sanitizeHTML(htmlString string) (string, error) {
    root, err := html.Parse(strings.NewReader(htmlString))
    if err != nil {
        return "", err
    }

    var f func(*html.Node)
    f = func(n *html.Node) {
        // 移除不在白名单中的标签
        if n.Type == html.ElementNode {
            if _, ok := allowedTags[n.Data]; !ok {
                n.Type = html.TextNode
                n.Data = "" // 移除标签内容
            } else {
                // 清理属性
                var attrs []html.Attribute
                for _, attr := range n.Attr {
                    if allowedAttributes[n.Data] == nil || allowedAttributes[n.Data][attr.Key] {
                        attrs = append(attrs, attr)
                    }
                }
                n.Attr = attrs
            }
        }

        // 递归处理子节点
        for c := n.FirstChild; c != nil; c = c.NextSibling {
            f(c)
        }
    }

    f(root)

    // 将 HTML 树重新序列化为字符串
    sanitizedHTML, err := html2text.RenderNode(root)
    if err != nil {
        return "", err
    }

    return sanitizedHTML, nil
}

func main() {
    untrustedHTML := `<p>This is a <b>bold</b> text with a <script>alert("XSS")</script> and <a href="https://example.com">link</a>.</p>`
    safeHTML, err := sanitizeHTML(untrustedHTML)
    if err != nil {
        fmt.Println("Error:", err)
        return
    }
    fmt.Println("Original HTML:", untrustedHTML)
    fmt.Println("Sanitized HTML:", safeHTML)
}