Code refactoring related to message handling and retry logic. (#3745)

Release.md

@@ -1,3 +1,4 @@
 ### Fixes
 
 * frpc: Return code 1 when the first login attempt fails and exits.
+* When auth.method is `oidc` and auth.additionalScopes contains `HeartBeats`, if obtaining AccessToken fails, the application will be unresponsive.

client/admin_api.go

@@ -144,7 +144,14 @@ func (svr *Service) apiStatus(w http.ResponseWriter, _ *http.Request) {
 		_, _ = w.Write(buf)
 	}()
 
-	ps := svr.ctl.pm.GetAllProxyStatus()
+	svr.ctlMu.RLock()
+	ctl := svr.ctl
+	svr.ctlMu.RUnlock()
+	if ctl == nil {
+		return
+	}
+
+	ps := ctl.pm.GetAllProxyStatus()
 	for _, status := range ps {
 		res[status.Type] = append(res[status.Type], NewProxyStatusResp(status, svr.cfg.ServerAddr))
 	}