重命名客户端相关术语为节点；移动 utils 包到根路径；优化网关对节点各种连接状态的处理，并在节点断联后统一清理资源

utils/sync.go

@@ -0,0 +1,44 @@
+package utils
+
+import (
+	"sync"
+	"sync/atomic"
+)
+
+type WaitGroup interface {
+	Add(delta int)
+	Done()
+	Wait()
+}
+
+type CountWaitGroup struct {
+	wg  sync.WaitGroup
+	num atomic.Int64
+}
+
+func (c *CountWaitGroup) Add(delta int) {
+	c.wg.Add(delta)
+	c.num.Add(int64(delta))
+}
+
+func (c *CountWaitGroup) Done() {
+	c.wg.Done()
+	c.num.Add(-1)
+}
+
+func (c *CountWaitGroup) Wait() {
+	c.wg.Wait()
+}
+
+func (c *CountWaitGroup) Count() uint64 {
+	return uint64(c.num.Load())
+}
+
+func WgWait[T WaitGroup](wg T) <-chan struct{} {
+	ch := make(chan struct{})
+	go func() {
+		wg.Wait()
+		ch <- struct{}{}
+	}()
+	return ch
+}