fix: 按 K-00 约定修复 Go SDK 断线重交与退避

sdk/go/lru.go

@@ -0,0 +1,72 @@
+package nixmsg
+
+import "container/list"
+
+type lruEntry struct {
+	key string
+	val any
+}
+
+// lruCache 固定容量 LRU，删除时同步移除链表节点。
+type lruCache struct {
+	cap int
+	ll  *list.List
+	m   map[string]*list.Element
+}
+
+func newLRU(cap int) *lruCache {
+	if cap <= 0 {
+		cap = 10000
+	}
+	return &lruCache{
+		cap: cap,
+		ll:  list.New(),
+		m:   make(map[string]*list.Element),
+	}
+}
+
+func (c *lruCache) Get(key string) (any, bool) {
+	el, ok := c.m[key]
+	if !ok {
+		return nil, false
+	}
+	c.ll.MoveToFront(el)
+	return el.Value.(*lruEntry).val, true
+}
+
+func (c *lruCache) Put(key string, val any) {
+	if el, ok := c.m[key]; ok {
+		el.Value.(*lruEntry).val = val
+		c.ll.MoveToFront(el)
+		return
+	}
+	el := c.ll.PushFront(&lruEntry{key: key, val: val})
+	c.m[key] = el
+	for c.ll.Len() > c.cap {
+		back := c.ll.Back()
+		if back == nil {
+			break
+		}
+		ent := back.Value.(*lruEntry)
+		c.ll.Remove(back)
+		delete(c.m, ent.key)
+	}
+}
+
+func (c *lruCache) Delete(key string) {
+	el, ok := c.m[key]
+	if !ok {
+		return
+	}
+	c.ll.Remove(el)
+	delete(c.m, key)
+}
+
+func (c *lruCache) Len() int {
+	return c.ll.Len()
+}
+
+func (c *lruCache) Has(key string) bool {
+	_, ok := c.m[key]
+	return ok
+}