uri.go
func (u *URI) Scheme() []byte {
	scheme := u.scheme
	if len(scheme) == 0 {
		scheme = strHTTP
	}
	return scheme
}
func (u *URI) Scheme() []byte {
	scheme := u.scheme
	if len(scheme) == 0 {
		scheme = strHTTP
	}
	return scheme
}
// 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.