get fresh () {
    const method = this.method
    const s = this.ctx.status

    // GET or HEAD for weak freshness validation only
    if (method !== 'GET' && method !== 'HEAD') return false

    // 2xx or 304 as per rfc2616 14.26
    if ((s >= 200 && s < 300) || s === 304) {
      return fresh(this.header, this.response.header)
    }

    return false
  }
Check if the request is fresh, aka
Last-Modified and/or the ETag
still match.

@return {Boolean}
@api public