message: Update hello_world.rs example
diff: //! cargo run --example hello-world --release --features "cranelift"
  //! ```
  -use wasmer::{imports, wat2wasm, Function, Instance, Module, Store, TypedFunction};
  +use wasmer::{
  + imports, wat2wasm, Context, ContextMut, Function, Instance, Module, Store, TypedFunction,
  +};
  use wasmer_compiler::Universal;
  use wasmer_compiler_cranelift::Cranelift;
  @@ -50,11 +52,13 @@ fn main() -> anyhow::Result<()> {
  // A `Module` is a compiled WebAssembly module that isn't ready to execute yet.
  let module = Module::new(&store, wasm_bytes)?;
  - // Next we'll set up our `Module` so that we can execute it.
  + // Next we'll set up our `Module` so that we can execute it. First, create
  + // a `Context` in which to instantiate our `Module`.
  + let mut context = Context::new(&store, ());
  // We define a function to act as our "env" "say_hello" function imported in the
  // Wasm program above.
  - fn say_hello_world() {
  + fn say_hello_world(ctx: ContextMut<'_, ()>) {
  println!("Hello, world!")
  }
  @@ -63,7 +67,7 @@ fn main() -> anyhow::Result<()> {
  // We use the default namespace "env".
  "env" => {
  // And call our function "say_hello".
  - "say_hello" => Function::new_native(&store, say_hello_world),
  + "say_hello" => Function::new_native(&mut context, say_hello_world),
  }
  };
  @@ -71,17 +75,18 @@ fn main() -> anyhow::Result<()> {
  //
  // An `Instance` is a compiled WebAssembly module that has been set up
  // and is ready to execute.
  - let instance = Instance::new(&module, &import_object)?;
  + let instance = Instance::new(&mut context, &module, &import_object)?;
  // We get the `TypedFunction` with no parameters and no results from the instance.
  //
  // Recall that the Wasm module exported a function named "run", this is getting
  // that exported function from the `Instance`.
  - let run_func: TypedFunction<(), ()> = instance.exports.get_native_function("run")?;
  + let run_func: TypedFunction<(), ()> =
  + instance.exports.get_native_function(&mut context, "run")?;
  // Finally, we call our exported Wasm function which will call our "say_hello"
  // function and return.
  - run_func.call()?;
  + run_func.call(&mut context)?;
  Ok(())
  }
  