public class App {

    public static void main(String[] args) throws Exception {
        RatpackServer.start(s -> s
             .serverConfig( configBuilder -> configBuilder
                .findBaseDir()
                .props("db.properties")
                .require("/database", Settings.class)
             )
             .registry(Guice.registry( bindings -> bindings
                     .module(HikariModule.class, hm -> {
                         hm.setDataSourceClassName("org.postgresql.ds.PGSimpleDataSource");
                         hm.addDataSourceProperty("url", "jdbc:postgresql://localhost:5433/ratpack");
                         hm.setUsername("postgres");
                         hm.setPassword("postgres");
                     }).bind(DatabaseInit.class)
             ))
             .handlers( chain -> chain
                    ...
             )
        );
    }
}