code: func CompressHandlerLevel(h RequestHandler, level int) RequestHandler {
  	return func(ctx *RequestCtx) {
  		h(ctx)
  		if ctx.Request.Header.HasAcceptEncodingBytes(strGzip) {
  			ctx.Response.gzipBody(level)
  		} else if ctx.Request.Header.HasAcceptEncodingBytes(strDeflate) {
  			ctx.Response.deflateBody(level)
  		}
  	}
  }
docs: // CompressHandlerLevel returns RequestHandler that transparently compresses
  // response body generated by h if the request contains 'gzip' or 'deflate'
  // 'Accept-Encoding' header.
  //
  // Level is the desired compression level:
  //
  //     * CompressNoCompression
  //     * CompressBestSpeed
  //     * CompressBestCompression
  //     * CompressDefaultCompression
  //     * CompressHuffmanOnly