feat: cache add single-flight and timing-wheel.

pkg/common/localcache/singleflight.go

@@ -0,0 +1,43 @@
+package localcache
+
+import "sync"
+
+type call[K comparable, V any] struct {
+	wg  sync.WaitGroup
+	val V
+	err error
+}
+
+type SingleFlight[K comparable, V any] struct {
+	mu sync.Mutex
+	m  map[K]*call[K, V]
+}
+
+func NewSingleFlight[K comparable, V any]() *SingleFlight[K, V] {
+	return &SingleFlight[K, V]{m: make(map[K]*call[K, V])}
+}
+
+func (r *SingleFlight[K, V]) Do(key K, fn func() (V, error)) (V, error) {
+	r.mu.Lock()
+	if r.m == nil {
+		r.m = make(map[K]*call[K, V])
+	}
+	if c, ok := r.m[key]; ok {
+		r.mu.Unlock()
+		c.wg.Wait()
+		return c.val, c.err
+	}
+	c := new(call[K, V])
+	c.wg.Add(1)
+	r.m[key] = c
+	r.mu.Unlock()
+
+	c.val, c.err = fn()
+	c.wg.Done()
+
+	r.mu.Lock()
+	delete(r.m, key)
+	r.mu.Unlock()
+
+	return c.val, c.err
+}