Steps on how to organize a library in Rust

Cargo.toml

[package]
name = "graph"
version = "0.1.0"
authors = ["me"]
edition = "2020"

[lib]
name = "service"
path = "src/lib.rs"

[[bin]]
name = "graph"
path = "src/main.rs"

[dependencies]

lib.rs

// src/lib.rs
// Any useful functions
pub fn printer_service(s: &str){
    let s = format!("Some useful lib function on {} called", s);
    println!("{}", s)
}

// Any useful tests
#[cfg(test)]
mod tests {
    #[test]
    fn it_works() {
        assert_eq!(2 + 2, 4);
    }
}

main.rs

// src/main.rs
// Main function
use service::printer_service;

pub fn main(){
    printer_service("my test func");
}