Use clap for cli

src/main.rs

@@ -1,31 +1,30 @@
 mod health;
 mod routes;
 
+use clap::Parser;
 use dotenv::dotenv;
 use health::HealthState;
 use rocket::fs::FileServer;
 use rocket_dyn_templates::Template;
+use std::io;
+use std::path::PathBuf;
 use std::sync::Arc;
 use std::time::Duration;
-use std::{env, io};
 use tokio::{fs, task, time::sleep};
 
-fn start_poller(state: Arc<HealthState>) {
-    task::spawn(async move {
-        loop {
-            state.update().await;
-            sleep(Duration::from_secs(state.config.update_period)).await;
-        }
-    });
+#[derive(Parser)]
+struct Opt {
+    /// Path to the config file.
+    #[clap(short, long, env = "CONFIG_PATH", default_value = "config.ron")]
+    config: PathBuf,
 }
 
 #[rocket::main]
 async fn main() -> io::Result<()> {
     dotenv().ok();
+    let opt = Opt::parse();
 
-    let config_path = env::var("CONFIG_PATH").unwrap_or("config.ron".into());
-
-    let config = fs::read_to_string(&config_path)
+    let config = fs::read_to_string(&opt.config)
         .await
         .expect("failed to read config file");
     let config = ron::from_str(&config).expect("failed to parse config file");
@@ -43,3 +42,12 @@ async fn main() -> io::Result<()> {
 
     Ok(())
 }
+
+fn start_poller(state: Arc<HealthState>) {
+    task::spawn(async move {
+        loop {
+            state.update().await;
+            sleep(Duration::from_secs(state.config.update_period)).await;
+        }
+    });
+}