_fastGet(rPath, lPath, opts, addListeners = true) {
    let listeners;
    return new Promise((resolve, reject) => {
      if (addListeners) {
        listeners = addTempListeners(this, '_fastGet', reject);
      }
      if (haveConnection(this, '_fastGet', reject)) {
        this.sftp.fastGet(rPath, lPath, opts, (err) => {
          if (err) {
            reject(this.fmtError(`${err.message} Remote: ${rPath} Local: ${lPath}`));
          }
          resolve(`${rPath} was successfully download to ${lPath}!`);
        });
      }
    }).finally(() => {
      if (addListeners) {
        removeTempListeners(this, listeners, '_fastGet');
      }
    });
  }
Use SSH2 fastGet for downloading the file.
Downloads a file at remotePath to localPath using parallel reads
for faster throughput.

WARNING: The functionality of fastGet is heavily dependent on the capabilities
of the remote SFTP server. Not all sftp server support or fully support this
functionality. See the Platform Quirks & Warnings section of the README.

@param {String} remotePath
@param {String} localPath
@param {Object} options
@return {Promise<String>} the result of downloading the file