Dessa forma, você pode criar um token com um prazo de expiração, digamos, de 1 semana. E então, quando o usuário voltar no dia seguinte com o token, você sabe que ele ainda está logado no seu sistema.

    // then we know it must have given a pending toString value earlier. If not, then the future
    // completed after the timeout expired, and the message might be success.
    if (isDone()) {
      throw new TimeoutException(message + " but future completed as timeout expired");
    }
    throw new TimeoutException(message + " for " + futureToString);
  }

  @ParametricNullness

                ErrorCategory.AUTHENTICATION, false), INVALID_CREDENTIALS("Invalid credentials", ErrorCategory.AUTHENTICATION,
                        false), SESSION_EXPIRED("Session expired", ErrorCategory.AUTHENTICATION, true),

        // File system errors
        FILE_NOT_FOUND("File not found", ErrorCategory.FILE_SYSTEM, false), PATH_NOT_FOUND("Path not found", ErrorCategory.FILE_SYSTEM,

			z.ContentEncoding, bts, err = msgp.ReadStringBytes(bts)
			if err != nil {
				err = msgp.WrapError(err, "ContentEncoding")
				return
			}
		case "Expires":
			z.Expires, bts, err = msgp.ReadTimeBytes(bts)
			if err != nil {
				err = msgp.WrapError(err, "Expires")
				return
			}
		case "CacheControl":
			z.CacheControl, bts, err = msgp.ReadStringBytes(bts)
			if err != nil {

Nesse caso, você poderia querer documentar como essa API externa *deveria* ser. Que *operação de rota* ela deveria ter, que corpo ela deveria esperar, que resposta ela deveria retornar, etc.

## Um aplicativo com callbacks { #an-app-with-callbacks }

Vamos ver tudo isso com um exemplo.

Imagine que você desenvolve um aplicativo que permite criar faturas.

  /** The HTTP {@code ETag} header field name. */
  public static final String ETAG = "ETag";

  /** The HTTP {@code Expires} header field name. */
  public static final String EXPIRES = "Expires";

  /** The HTTP {@code Last-Modified} header field name. */
  public static final String LAST_MODIFIED = "Last-Modified";

  /** The HTTP {@code Link} header field name. */

                return "lang,role,label,anchor,virtual_host";
            }

            @Override
            public String getIndexAdminDateFields() {
                return "expires,created,timestamp,last_modified";
            }

            @Override
            public String getIndexAdminIntegerFields() {
                return "";
            }

            @Override

    * A "token" is just a string with some content that we can use later to verify this user.
    * Normally, a token is set to expire after some time.
        * So, the user will have to log in again at some point later.
        * And if the token is stolen, the risk is less. It is not like a permanent key that will work forever (in most of the cases).

                    if (time > maxAge || time < 0) {
                        if (logger.isDebugEnabled()) {
                            logger.debug("role info is expired: {} > {}", time, maxAge);
                        }
                        return;
                    }
                } catch (final NumberFormatException e) {

	ArgsList []*Expression `parser:"\"(\" (@@ (\",\" @@)*)?\")\""`
}

// CountFunc represents the COUNT sql function
type CountFunc struct {
	StarArg bool        `parser:" \"COUNT\" \"(\" ( @\"*\"?"`
	ExprArg *Expression `parser:" @@? )! \")\""`
}

// CastFunc represents CAST sql function
type CastFunc struct {
	Expr     *Expression `parser:" \"CAST\" \"(\" @@ "`