web_backend: protect jwt cache with a mutex

src/web_service/web_backend.cpp

@@ -24,6 +24,7 @@ Client::JWTCache Client::jwt_cache{};
 
 Client::Client(const std::string& host, const std::string& username, const std::string& token)
     : host(host), username(username), token(token) {
+    std::lock_guard<std::mutex> lock(jwt_cache.mutex);
     if (username == jwt_cache.username && token == jwt_cache.token) {
         jwt = jwt_cache.jwt;
     }
@@ -116,6 +117,7 @@ void Client::UpdateJWT() {
         if (result.result_code != Common::WebResult::Code::Success) {
             LOG_ERROR(WebService, "UpdateJWT failed");
         } else {
+            std::lock_guard<std::mutex> lock(jwt_cache.mutex);
             jwt_cache.username = username;
             jwt_cache.token = token;
             jwt_cache.jwt = jwt = result.returned_data;

src/web_service/web_backend.h

@@ -5,7 +5,7 @@
 #pragma once
 
 #include <functional>
-#include <future>
+#include <mutex>
 #include <string>
 #include <tuple>
 #include <httplib.h>
@@ -81,6 +81,7 @@ private:
     std::unique_ptr<httplib::Client> cli;
 
     struct JWTCache {
+        std::mutex mutex;
         std::string username;
         std::string token;
         std::string jwt;