router handler: add cache for sd service

internal/util/cache/cache.go

@@ -0,0 +1,64 @@
+package cache
+
+import (
+	"sync"
+	"time"
+)
+
+type Item struct {
+	v          interface{}
+	expiration int64
+}
+
+func NewItem(v interface{}, d time.Duration) *Item {
+	var expiration int64
+	if d > 0 {
+		expiration = time.Now().Add(d).UnixNano()
+	}
+
+	return &Item{
+		v:          v,
+		expiration: expiration,
+	}
+}
+
+func (p *Item) Expired() bool {
+	if p == nil {
+		return true
+	}
+	return p.expiration > 0 && time.Now().UnixNano() > p.expiration
+}
+
+func (p *Item) Value() interface{} {
+	if p == nil {
+		return nil
+	}
+	return p.v
+}
+
+type Cache struct {
+	items           map[string]*Item
+	cleanupInterval time.Duration
+	mu              sync.RWMutex
+}
+
+func NewCache(cleanupInterval time.Duration) *Cache {
+	return &Cache{
+		cleanupInterval: cleanupInterval,
+		items:           make(map[string]*Item),
+	}
+}
+
+func (c *Cache) Set(key string, item *Item) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	c.items[key] = item
+}
+
+func (c *Cache) Get(key string) *Item {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+
+	return c.items[key]
+}