Adding example diesel r2d2

Author: manuelarte

Cargo.lock

@@ -0,0 +1,12 @@
+[package]
+edition.workspace = true
+name = "embedded_async_diesel_r2d2"
+publish = false
+license.workspace = true
+version.workspace = true
+
+[dependencies]
+postgresql_embedded = { path = "../../postgresql_embedded" }
+tokio = { workspace = true, features = ["full"] }
+diesel = { version = "2.2.1", features = ["postgres", "r2d2"] }
+r2d2_postgres = "0.18.1"

examples/embedded_async_diesel_r2d2/Cargo.toml

@@ -0,0 +1,44 @@
+#![forbid(unsafe_code)]
+#![deny(clippy::pedantic)]
+
+use diesel::r2d2::{ConnectionManager, Pool};
+use diesel::PgConnection;
+use postgresql_embedded::{PostgreSQL, Result, Settings, VersionReq};
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let settings = Settings {
+        version: VersionReq::parse("=16.4.0")?,
+        ..Default::default()
+    };
+    let mut postgresql = PostgreSQL::new(settings);
+    postgresql.setup().await?;
+    postgresql.start().await?;
+
+    let database_name = "test";
+    postgresql.create_database(database_name).await?;
+    postgresql.database_exists(database_name).await?;
+
+    {
+        let database_url = postgresql.settings().url(database_name);
+        let manager = ConnectionManager::<PgConnection>::new(database_url);
+        let _pool = Pool::builder()
+            .test_on_check_out(true)
+            .build(manager)
+            .expect("Could not build connection pool");
+    }
+
+    postgresql.drop_database(database_name).await?;
+
+    postgresql.stop().await
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_main() -> Result<()> {
+        main()
+    }
+}