maximize fd limit

Cargo.toml

@@ -104,6 +104,9 @@ async-trait = "0.1.68"
 
 sd-notify = { version = "0.4.1", optional = true }
 
+[target.'cfg(unix)'.dependencies]
+nix = { version = "0.26.2", features = ["resource"] }
+
 [features]
 default = ["conduit_bin", "backend_sqlite", "backend_rocksdb", "systemd"]
 #backend_sled = ["sled"]