string.go
func StringFind(s, token string) (remainder string, found bool) {
	i := strings.Index(s, token)
	if i == -1 {
		return s, false
	}
	return s[i+len(token):], true
}
func StringFind(s, token string) (remainder string, found bool) {
	i := strings.Index(s, token)
	if i == -1 {
		return s, false
	}
	return s[i+len(token):], true
}
// StringFind returns in found if token has been found in s,
// and returns the remaining string afte token in remainder.
// The whole string s will be returned if found is false.