fetchFileList() {
return new Promise((resolve, reject) => {
  const sshClient = new Client();
  let isReady = false;
  logger.info("fetchFileList making SF connection");
  sshClient.on("ready", () => {
    isReady = true;
    logger.info("Ready");
    sshClient.sftp((err, sftp) => {
      if (err) {
        logger.error("Some error occoured ", { err });
        reject("Error establishing sftp connection");
      }
      logger.info("Sftp connection is successful");
      sftp.readdir(CONST.EXTRACT.FTP_DIRECTORY, (err, files) => {
        if (err) {
          reject(new CustomError("Sftp read dir", err));
        }
        // Read all file 'formats' from entity db
        sortFilesByTables(files)
          .then(result => {
            resolve({ sshClient, sftp, result });
          })
          .catch(err => {
            reject(new CustomError("Error sorting files by tables ", err));
          });
      });
    });
  });
  sshClient.on("error", err => {
    logger.error("Error connecting to sftp server ", err);
    webHook
      .send(
        utils.composeSlackMessage(
          "Error connecting to sftp server",
          CONST.EXPORT.SLACK_MESSAGE_TYPES.ERROR,
          err
        )
      )
      .catch(err => logger.error("Webkook catch ", err));
    reject(new CustomError("Error connecting to sftp server ", err));
  });

  sshClient.on("end", () => {
    if (!isReady) {
      logger.error(
        "fetchFileList on end Callback could not establish sftp connection"
      );
      reject(
        "fetchFileList on end Callback could not establish sftp connection"
      );
    }
  });

  sshClient.connect({
    host: ftpCredentials.host,
    port: ftpCredentials.port,
    username: ftpCredentials.username,
    password: ftpCredentials.password,
    readyTimeout: 90000
  });
});