error: 'id' is declared as an argument...
   --> src/main.rs:8:9
    |
  8 | #[get("/<id>")]
    |         ^^^^

  error: ...but isn't in the function signature.
    --> src/main.rs:9:1
     |
  9  |   fn hello() -> &'static str {
     |  _^ starting here...
  10 | |     "Hello, world!"
  11 | | }
     | |_^ ...ending here