Update README with usage documentation (#13)

README.md

@@ -10,3 +10,81 @@
 
 Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, 
 shall be licensed as above, without any additional terms or conditions.
+
+## Usage
+
+Add the crate, with [deadpool](https://docs.rs/deadpool/latest/deadpool/index.html) or [bb8](https://docs.rs/bb8/latest/bb8/). If you haven't already, also add your shuttle dependencies. 
+
+This example demonstrates usage with postgres and deadpool.
+
+```sh
+cargo add --git "https://github.com/aumetra/shuttle-diesel-async" -F "deadpool"
+# or
+cargo add --git "https://github.com/aumetra/shuttle-diesel-async" -F "bb8"
+
+## diesel dependencies
+cargo add diesel -F postgres
+cargo add diesel-async -F postgres -F deadpool
+
+## other shuttle dependencies you may want
+cargo add shuttle-runtime  # or cargo add shuttle-runtime --no-default-features
+# to load secrets, like the DATABASE_URL from your environment
+cargo add shuttle-secrets
+
+# the following example demonstrates with shuttle-axum
+cargo add axum 
+cargo add shuttle-axum
+```
+
+Adjust your `main` function, (We will use `ShuttleAxum` as example) to set up your database connection, and add fields in your `Secrets.toml` accordingly.
+
+Secrets.toml:
+
+```toml
+DB_PASSWORD="postgres" # or whatever you have it set to
+DB_PORT="5432" # default port for postgres
+```
+
+```rust
+use diesel::result::Error;
+use diesel_async::{
+  pooled_connection::{deadpool::Pool, AsyncDieselConnectionManager},
+  AsyncConnection, RunQueryDsl,
+};
+
+#[derive(Clone)]
+pub struct SharedState {
+  pub pool: Pool<AsyncPgConnection>,
+}
+
+#[shuttle_runtime::main]
+async fn main(
+  #[shuttle_secrets::Secrets] secret_store: shuttle_secrets::SecretStore,
+  // shuttle will provision the database connection
+  #[shuttle_shared_db::Postgres(
+    local_uri = "postgres://postgres:{secrets.DB_PASSWORD}@localhost:{secrets.DB_PORT}/postgres"
+  )]
+  conn_str: String,
+) -> shuttle_axum::ShuttleAxum {
+
+  let config = AsyncDieselConnectionManager::<diesel_async::AsyncPgConnection>::new(conn_str);
+  let pool = Pool::builder(config).build().unwrap();
+  let shared_state = SharedState { pool };
+
+  let router = Router::new()
+    .route("/", get(handler))
+    .with_state(shared_state);
+
+  Ok(router.into())
+}
+
+use axum::extract::State;
+async fn handler(State(state): State<SharedState>) {
+  // get the connection from the pool
+  let mut conn = state.pool.get().await.unwrap();
+  // and you're good to go.
+  crate::schema::your_table_name::dsl::your_table_name.select(YourTableStruct::as_select()).load(conn).await.unwrap()
+}
+```
+
+Refer to [this example](https://github.com/tokio-rs/axum/blob/main/examples/diesel-async-postgres/src/main.rs) for further direction on using diesel, and the [shuttle docs](https://docs.shuttle.rs/resources/shuttle-shared-db#connection-string) on `shuttle-shared-db`.