bevy tutorial add plugins step

Cargo.toml

[package]
name = "game"
version = "0.1.0"
authors = ["maxwell"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
bevy = "0.1.2" # make sure this is the latest version

main.rs

use bevy::prelude::*;

struct Person;
struct Name(String);

fn hello_world() {
    println!("hello world!");
}

fn add_people(mut commands: Commands) {
    commands
    .spawn((Person, Name("Elaina Proctor".to_string())))
    .spawn((Person, Name("Renzo Hume".to_string())))
    .spawn((Person, Name("Zayna Nieves".to_string())));
}

fn greet_people(person: &Person, name: &Name) {
    println!("hello {}!", name.0);
}

fn main() {
    App::build()
    .add_default_plugins()
    .add_startup_system(add_people.system())
    .add_system(hello_world.system())
    .add_system(greet_people.system())
    .run();
}

stack trace

~/programs/game$ env RUST_BACKTRACE=full cargo run
warning: unused variable: `person`
  --> src/main.rs:17:17
   |
17 | fn greet_people(person: &Person, name: &Name) {
   |                 ^^^^^^ help: if this is intentional, prefix it with an underscore: `_person`
   |
   = note: `#[warn(unused_variables)]` on by default

warning: 1 warning emitted

    Finished dev [unoptimized + debuginfo] target(s) in 0.20s
     Running `target/debug/game`
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /home/maxwell/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_wgpu-0.1.0/src/wgpu_renderer.rs:22:23
stack backtrace:
   0:     0x555bd6641fe5 - backtrace::backtrace::libunwind::trace::ha215bbf14e328799
                               at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1:     0x555bd6641fe5 - backtrace::backtrace::trace_unsynchronized::h3384b099b135857a
                               at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/mod.rs:66
   2:     0x555bd6641fe5 - std::sys_common::backtrace::_print_fmt::hfec93740f7294682
                               at src/libstd/sys_common/backtrace.rs:78
   3:     0x555bd6641fe5 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h5fe20777f4174074
                               at src/libstd/sys_common/backtrace.rs:59
   4:     0x555bd666e37c - core::fmt::write::he14c3177144df275
                               at src/libcore/fmt/mod.rs:1076
   5:     0x555bd663e233 - std::io::Write::write_fmt::h8e26323bfab8bcc5
                               at src/libstd/io/mod.rs:1537
   6:     0x555bd6644dc0 - std::sys_common::backtrace::_print::h9cfa4c87526ba064
                               at src/libstd/sys_common/backtrace.rs:62
   7:     0x555bd6644dc0 - std::sys_common::backtrace::print::h94936584848b3272
                               at src/libstd/sys_common/backtrace.rs:49
   8:     0x555bd6644dc0 - std::panicking::default_hook::{{closure}}::h733b20cc9b496e46
                               at src/libstd/panicking.rs:198
   9:     0x555bd6644b0c - std::panicking::default_hook::h556d8cff6c12a651
                               at src/libstd/panicking.rs:218
  10:     0x555bd66453f7 - std::panicking::rust_panic_with_hook::ha0c7ca5b39baa9d5
                               at src/libstd/panicking.rs:486
  11:     0x555bd6644ffb - rust_begin_unwind
                               at src/libstd/panicking.rs:388
  12:     0x555bd666c001 - core::panicking::panic_fmt::h106d7128cbbc7cd2
                               at src/libcore/panicking.rs:101
  13:     0x555bd666bf4d - core::panicking::panic::hfe03c118d2519816
                               at src/libcore/panicking.rs:56
  14:     0x555bd54b379f - core::option::Option<T>::unwrap::h44434fcbe4098c48
                               at /rustc/d3fb005a39e62501b8b0b356166e515ae24e2e54/src/libcore/macros/mod.rs:10
  15:     0x555bd546e676 - bevy_wgpu::wgpu_renderer::WgpuRenderer::new::{{closure}}::h4306164a44baab1f
                               at /home/maxwell/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_wgpu-0.1.0/src/wgpu_renderer.rs:22
  16:     0x555bd54ce2b4 - <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll::h4eba355fd256caa1
                               at /rustc/d3fb005a39e62501b8b0b356166e515ae24e2e54/src/libcore/future/mod.rs:73
  17:     0x555bd5469286 - pollster::block_on::hcaec530150895f97
                               at /home/maxwell/.cargo/registry/src/github.com-1ecc6299db9ec823/pollster-0.2.0/src/lib.rs:64
  18:     0x555bd544204e - bevy_wgpu::wgpu_render_system::h66255b159df9f913
                               at /home/maxwell/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_wgpu-0.1.0/src/lib.rs:35
  19:     0x555bd5441f0a - <bevy_wgpu::WgpuPlugin as bevy_app::plugin::Plugin>::build::h2cbdcb26dfdfdf41
                               at /home/maxwell/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_wgpu-0.1.0/src/lib.rs:22
  20:     0x555bd54357e4 - bevy_app::app_builder::AppBuilder::add_plugin::h227b6619099c1a69
                               at /home/maxwell/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_app-0.1.0/src/app_builder.rs:235
  21:     0x555bd54377b5 - <bevy_app::app_builder::AppBuilder as bevy::add_default_plugins::AddDefaultPlugins>::add_default_plugins::h922b97a71f4b1ce3
                               at /home/maxwell/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy-0.1.2/src/add_default_plugins.rs:33
  22:     0x555bd5431771 - game::main::heabd118ce19758c6
                               at src/main.rs:22
  23:     0x555bd542b6db - std::rt::lang_start::{{closure}}::h6d03a314088763ff
                               at /rustc/d3fb005a39e62501b8b0b356166e515ae24e2e54/src/libstd/rt.rs:67
  24:     0x555bd6645888 - std::rt::lang_start_internal::{{closure}}::hefb489d56a389b75
                               at src/libstd/rt.rs:52
  25:     0x555bd6645888 - std::panicking::try::do_call::hb2bfa58b743656f1
                               at src/libstd/panicking.rs:297
  26:     0x555bd6645888 - std::panicking::try::haaa85a89ce3784c3
                               at src/libstd/panicking.rs:274
  27:     0x555bd6645888 - std::panic::catch_unwind::h49baa277f74e60cb
                               at src/libstd/panic.rs:394
  28:     0x555bd6645888 - std::rt::lang_start_internal::h7aa2f6739b31fe58
                               at src/libstd/rt.rs:51
  29:     0x555bd542b6b7 - std::rt::lang_start::h16175c9b03f4a3e9
                               at /rustc/d3fb005a39e62501b8b0b356166e515ae24e2e54/src/libstd/rt.rs:67
  30:     0x555bd543188a - main
  31:     0x7f773a7e5b97 - __libc_start_main
  32:     0x555bd542b42a - _start
  33:                0x0 - <unknown>