* https://fasterthanli.me/blog/2020/a-half-hour-to-learn-rust/ - 이걸 다 읽고
* https://github.com/rust-lang/rustlings/ - Rustling을 한다
* https://doc.rust-lang.org/stable/rust-by-example/ - Rust By Example을 읽고
* https://doc.rust-lang.org/book/ - 마지막으로 "the book"을 읽는다.
ERROR's and HOW TO FIX:
* an `extern crate` loading macros must be at the crate root` - move macros as guided.
* cannot find derive macro deserialize in this scope