client: fix Do hangs when configure host client fails (#1514)

client.go

@@ -527,6 +527,7 @@ func (c *Client) Do(req *Request, resp *Response) error {
 
  if c.ConfigureClient != nil {
  if err := c.ConfigureClient(hc); err != nil {
+ c.mLock.Unlock()
  return err
  }
  }

client_test.go

@@ -2734,6 +2734,30 @@ func TestClientTLSHandshakeTimeout(t *testing.T) {
  }
 }
 
+func TestClientConfigureClientFailed(t *testing.T) {
+ t.Parallel()
+
+ c := &Client{
+ ConfigureClient: func(hc *HostClient) error {
+ return fmt.Errorf("failed to configure")
+ },
+ }
+
+ req := Request{}
+ req.SetRequestURI("http://example.com")
+
+ err := c.Do(&req, &Response{})
+ if err == nil {
+ t.Fatal("expected error (failed to configure)")
+ }
+
+ c.ConfigureClient = nil
+ err = c.Do(&req, &Response{})
+ if err != nil {
+ t.Fatalf("unexpected error: %v", err)
+ }
+}
+
 func TestHostClientMaxConnWaitTimeoutSuccess(t *testing.T) {
  t.Parallel()