code: function(client, key, ttl) {
      client.ttl(key, function(err, currentTtl) {
          if (currentTtl === -1) {
              // There is no expiry set on this key, set it
              client.expire(key, ttl);
          }
      });
  }
docs: Ensure the lock with the given key has a `ttl`. If it does not, the given expiry will be applied
  to it.
  
  @param   {RedisClient}   client  The Redis to use to apply the ttl
  @param   {string}        key     The key of the lock to check
  @param   {number}        ttl     If the lock does not have an expiry set, set this duration (in
  seconds)
  @api private