AppwriteException null, Connection refused (0)

minusFromDb() async {
    AppWriteLogic appwriteData = AppWriteLogic();
    appwriteData.appwriteEndpointProjectID();

    Future result = appwriteData.databases.updateDocument(
      databaseId: appwriteData.databaseID.toString(),
      collectionId: appwriteData.walletBalanceCollectionID.toString(),
      // documentId: walletDocumentID.toString(),
      documentId: "wallet_data_${userID}",
      // 
      // 
      data: {"current_wallet_balance": 100},
    );
    // 

    result.then((response) {
      print("object");
      // 
    }).catchError((error) {
      print(error);
    });
  }

  String endpoint = "http://localhost/v1";
  String projectId = 'project id';
  String variablesKey =
      "key from console";
  String walletBalanceCollectionID = "wallet balance collection";
  String databaseID = "database id";

//  create account, function instance
  Databases databases = Databases(client);

  Functions functions = Functions(client);

  late Account account;
// Functions functions = Functions(client);

//   pass in secret data
  appwriteEndpointProjectID() {
    client
        .setEndpoint(endpoint) // Your API Endpoint
        .setProject(projectId) // ID
        .setSelfSigned(status: true)
        .setKey(variablesKey);

    account = Account(client);
  }
}