You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: main.rs
    path of file: ./repos/mun/examples/rust-pong/src
    
    the code of the file until where you have to start completion: use ggez::{
    event::{self, EventHandler, KeyCode, KeyMods},
    graphics::{self, DrawMode, DrawParam, FilterMode, Mesh, MeshBuilder, Rect, Text},
    mint as na,
    mint::Point2,
    Context, ContextBuilder, GameError, GameResult,
};
use mun_runtime::{RootedStruct, Runtime, StructRef};
use rand::Rng;

extern "C" fn rand_f32() -> f32 {
    let mut 
    
fn main() {
    let (ctx, event_loop) = ContextBuilder::new("Pong", "Mun Team")
        .build()
        .expect("Failed to initialize ggez");

    let builder = Runtime::builder("mun/target/mod.munlib")
        .insert_fn("rand_f32", rand_f32 as extern "C" fn() -> f32);

    let runtime = unsafe { builder.finish() }.expect("Failed to load munlib");

    let state: StructRef = runtime.invoke("new_state", ()).unwrap();
    let state = state.root();
    let pong = PongGame { runtime, state };

    event::run(ctx, event_loop, pong);
}