Add lock to InvalidSession

src/Discord.Net.WebSocket/DiscordSocketClient.cs

@@ -520,7 +520,15 @@ namespace Discord.WebSocket
                             _sessionId = null;
                             _lastSeq = 0;
 
-                            await ApiClient.SendIdentifyAsync(shardID: ShardId, totalShards: TotalShards, guildSubscriptions: _guildSubscriptions, gatewayIntents: _gatewayIntents).ConfigureAwait(false);
+                            await _shardedClient.AcquireIdentifyLockAsync(ShardId, _connection.CancelToken).ConfigureAwait(false);
+                            try
+                            {
+                                await ApiClient.SendIdentifyAsync(shardID: ShardId, totalShards: TotalShards, guildSubscriptions: _guildSubscriptions, gatewayIntents: _gatewayIntents).ConfigureAwait(false);
+                            }
+                            finally
+                            {
+                                _shardedClient.ReleaseIdentifyLock();
+                            }
                         }
                         break;
                     case GatewayOpCode.Reconnect: