code: function tokenExists(username, token, done) {
    return getTokenHashes(username, function(getTokensErr, hashes) {
      if (getTokensErr) {
        return done(getTokensErr);
      }
  
      if (!hashes || !hashes.length) {
        return done(null, false);
      }
  
      let index = 0;
      let found = false;
  
      async.until(() => found || (index >= hashes.length), function(next) {
        bcrypt.compare(token, hashes[index++].uuid, function(err, match) {
          found = match;
          return next(err);
        });
      }, (err) => done(err, found ? hashes[index - 1] : undefined));
    });
  }
docs: Check if token exists. If found it is returned.
  
  @param {String} token
  @param {Function} done - done(err, tokenObj)