fix the problem: HostClient maybe delete when pendingClientRequests >…

… 0 (#1562)

* add the functions to get host clients

* add concurrency for client's HostClient map

* delete test code

* add lock in once block

* fix the problem: HostClient maybe delete when pendingClientRequests > 0

* fix the problem: HostClient maybe delete when pendingClientRequests > 0

---------

Co-authored-by: wangzhengkai.wzk <wangzhengkai.wzk@alibaba-inc.com>

client.go

@@ -501,6 +501,10 @@ func (c *Client) Do(req *Request, resp *Response) error {
 		m = c.ms
 	}
 	hc := m[string(host)]
+	if hc != nil {
+		atomic.AddInt32(&hc.pendingClientRequests, 1)
+		defer atomic.AddInt32(&hc.pendingClientRequests, -1)
+	}
 	c.mLock.RUnlock()
 	if hc == nil {
 		c.mLock.Lock()
@@ -545,12 +549,11 @@ func (c *Client) Do(req *Request, resp *Response) error {
 				startCleaner = true
 			}
 		}
+		atomic.AddInt32(&hc.pendingClientRequests, 1)
+		defer atomic.AddInt32(&hc.pendingClientRequests, -1)
 		c.mLock.Unlock()
 	}
 
-	atomic.AddInt32(&hc.pendingClientRequests, 1)
-	defer atomic.AddInt32(&hc.pendingClientRequests, -1)
-
 	if startCleaner {
 		go c.mCleaner(m)
 	}