code: func (req *Request) Body() []byte {
  	if req.bodyStream != nil {
  		bodyBuf := req.bodyBuffer()
  		bodyBuf.Reset()
  		_, err := copyZeroAlloc(bodyBuf, req.bodyStream)
  		req.closeBodyStream()
  		if err != nil {
  			bodyBuf.SetString(err.Error())
  		}
  	} else if req.onlyMultipartForm() {
  		body, err := marshalMultipartForm(req.multipartForm, req.multipartFormBoundary)
  		if err != nil {
  			return []byte(err.Error())
  		}
  		return body
  	}
  	return req.bodyBytes()
  }
docs: // Body returns request body.
  //
  // The returned body is valid until the request modification.