chore: add basic configuration handling

Currently, this will read configuration from environment variables only.
The `envy` library can attempt to deserialize any struct implementing
`serde::Deserialize` from environment variables, which is pretty neat.

Author: Chris Connelly

Cargo.lock

@@ -7,9 +7,11 @@ edition = "2021"
 
 [dependencies]
 axum = "0.4.2"
+envy = "0.4.2"
 juniper = "0.15.7"
 juniper_hyper = "0.8.0"
 parking_lot = "0.11.2"
+serde = { version = "1.0.131", features = ["derive"] }
 tokio = { version = "1.14.0", features = ["macros", "rt-multi-thread"] }
 tower = "0.4.11"
 tower-http = { version = "0.2.0", features = ["trace"] }

Cargo.toml

@@ -14,17 +14,25 @@ use axum::{
 use juniper::{EmptySubscription, RootNode};
 use tower::ServiceBuilder;
 use tower_http::trace::TraceLayer;
-use tracing::info;
+use tracing::{info, trace};
 use tracing_subscriber::EnvFilter;
 
 use self::graphql::{Context, Mutation, Query};
 
+#[derive(Debug, serde::Deserialize)]
+struct Config {
+    database_url: String,
+}
+
 #[tokio::main]
 async fn main() {
     tracing_subscriber::fmt()
         .with_env_filter(EnvFilter::from_default_env())
         .init();
 
+    let config: Config = envy::from_env().unwrap();
+    trace!("TODO: connect to {}", config.database_url);
+
     let context = Arc::new(Context::default());
     let root_node = Arc::new(RootNode::new(Query, Mutation, EmptySubscription::new()));