message: Use async/await readFile from util.
diff: // @flow
  import path from 'path';
  -import fs from 'fs';
  +import { readFile } from '../util/fs';
  import { debug } from '../logger';
  import type { $Request, $Response } from 'express';
  @@ -17,11 +17,11 @@ export const keysAccessMiddleware = (
  next();
  };
  -export default (req: $Request, res: $Response) => {
  +export default async (req: $Request, res: $Response) => {
  debug('Collecting client keys.');
  // TODO:
  // This should actually fetch ssh keys from the store.
  - const keys = fs.readFileSync(path.resolve(__dirname, 'keys.txt'));
  + const keys = await readFile(path.resolve(__dirname, 'keys.txt'), 'utf8');
  res.send(keys);
  };
  