Only parse environment variables and CLI arguments on startup

Environment variables and CLI arguments can only be changed with a
process restart, so there is no point in parsing them every time we hot
reload our configuration. Instead, we can put the parsed configuration
in a `LazyLock` which will be initialized when we first parse
configuration on startup and then re-used when we hot reload.

Author: Molter73

fact/src/config/mod.rs

@@ -3,6 +3,7 @@ use std::{
     net::SocketAddr,
     path::{Path, PathBuf},
     str::FromStr,
+    sync::LazyLock,
 };
 
 use anyhow::{bail, Context};
@@ -66,8 +67,8 @@ impl FactConfig {
             )?;
 
         // Once file configuration is handled, apply CLI arguments
-        let args = FactCli::try_parse()?;
-        config.update(&args.to_config());
+        static CLI_ARGS: LazyLock<FactConfig> = LazyLock::new(|| FactCli::parse().to_config());
+        config.update(&CLI_ARGS);
 
         Ok(config)
     }