improve sqlx example

inspired by #455

Cargo.lock

@@ -3623,17 +3623,6 @@ version = "0.5.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7fb9b38af92608140b86b693604b9ffcc5824240a484d1ecd4795bacb2fe88f3"
 
-[[package]]
-name = "listenfd"
-version = "0.3.5"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "809e514e2cb8a9624701346ea3e694c1766d76778e343e537d873c1c366e79a7"
-dependencies = [
- "libc",
- "uuid",
- "winapi 0.3.9",
-]
-
 [[package]]
 name = "local-channel"
 version = "0.1.2"
@@ -5780,7 +5769,6 @@ dependencies = [
  "dotenv",
  "env_logger 0.7.1",
  "futures",
- "listenfd",
  "log",
  "serde 1.0.130",
  "serde_json",