fix tokio dependency

Cargo.toml

 [package]
 name = "minipac"
-version = "0.3.0"
+version = "0.3.1"
 edition = "2018"
 repository = "https://gitlab.scd31.com/stephen/minipac"
 authors = ["Stephen D"]
@@ -16,7 +16,7 @@ thiserror = "1.0"
 rand = "0.8"
 zstd = "0.9"
 crc = "2.1"
-tokio = { version = "1.0", features = ["rt", "sync", "tracing"] }
+tokio = { version = "1.0", features = ["rt", "sync", "tracing", "time"] }
 
 [dev-dependencies]
 tokio = { version = "1", features = ["macros", "rt", "sync", "time"] }