Add rust implementation

src/config.rs

@@ -0,0 +1,45 @@
+use serde::Deserialize;
+
+fn get_env(env: &'static str) -> String {
+    std::env::var(env).unwrap_or_else(|_| panic!("Cannot get the {} env variable", env))
+}
+
+#[derive(Deserialize, Clone)]
+pub struct SourceConfig {
+    pub url: String,
+    pub proxy: Option<String>
+}
+
+pub struct Config {
+    pub api_key: String,
+
+    pub fl_sources: Vec<SourceConfig>,
+
+    pub book_library_api_key: String,
+    pub book_library_url: String,
+
+    pub converter_url: String,
+
+    pub sentry_dsn: String
+}
+
+impl Config {
+    pub fn load() -> Config {
+        Config {
+            api_key: get_env("API_KEY"),
+
+            fl_sources: serde_json::from_str(&get_env("FL_SOURCES")).unwrap(),
+
+            book_library_api_key: get_env("BOOK_LIBRARY_API_KEY"),
+            book_library_url: get_env("BOOK_LIBRARY_URL"),
+
+            converter_url: get_env("CONVERTER_URL"),
+
+            sentry_dsn: get_env("SENTRY_DSN")
+        }
+    }
+}
+
+lazy_static! {
+    pub static ref CONFIG: Config = Config::load();
+}