code: func (u *URI) Scheme() []byte {
  	scheme := u.scheme
  	if len(scheme) == 0 {
  		scheme = strHTTP
  	}
  	return scheme
  }
docs: // Scheme returns URI scheme, i.e. http of http://aaa.com/foo/bar?baz=123#qwe .
  //
  // Returned scheme is always lowercased.
  //
  // The returned value is valid until the next URI method call.