code: func (r *Request) RequestURI(uri string) *Request {
  	if r.err != nil {
  		return r
  	}
  	locator, err := url.Parse(uri)
  	if err != nil {
  		r.err = err
  		return r
  	}
  	r.pathPrefix = locator.Path
  	if len(locator.Query()) > 0 {
  		if r.params == nil {
  			r.params = make(url.Values)
  		}
  		for k, v := range locator.Query() {
  			r.params[k] = v
  		}
  	}
  	return r
  }
docs: // RequestURI overwrites existing path and parameters with the value of the provided server relative
  // URI.