add more optimizations to release builds

Cargo.toml

@@ -12,3 +12,12 @@ serde = { version = "1.0.158", features = ["derive"] }
 tokio = { version = "1", features = ["full"] }
 tokio-socks = "0.5.1"
 toml = "0.7.3"
+
+[profile.release]
+lto = true
+codegen-units = 1
+
+[profile.bench]
+# useful for profiling, but increases binary size,
+# so potentially bad for real experiments
+debug = true