Add mutex to control the number of goroutine looking up meta table

client.go

@@ -90,6 +90,9 @@ type client struct {
 	// regionReadTimeout is the maximum amount of time to wait for regionserver reply
 	regionReadTimeout time.Duration
 
+	// The lock to control meta table lookup
+	lock sync.Mutex
+
 	done      chan struct{}
 	closeOnce sync.Once
 

rpc.go

@@ -342,8 +342,10 @@ func (c *client) metaLookup(ctx context.Context,
 		return nil, "", err
 	}
 
+	c.lock.Lock()
 	scanner := c.Scan(rpc)
 	resp, err := scanner.Next()
+	c.lock.Unlock()
 	if err == io.EOF {
 		return nil, "", TableNotFound
 	}