Fix future feature

Cargo.toml

@@ -6,7 +6,7 @@ homepage = "https://github.com/al8n/wg"
 repository = "https://github.com/al8n/wg.git"
 documentation = "https://docs.rs/wg/"
 readme = "README.md"
-version = "0.8.0"
+version = "0.8.1"
 license = "MIT OR Apache-2.0"
 keywords = ["waitgroup", "async", "sync", "notify", "wake"]
 categories = ["asynchronous", "concurrency", "data-structures"]
@@ -18,10 +18,10 @@ std = ["triomphe?/default", "event-listener?/default", "futures-core?/default",
 triomphe = ["dep:triomphe"]
 parking_lot = ["dep:parking_lot"]
 
-future = ["event-listener", "pin-project-lite"]
+future = ["event-listener", "pin-project-lite", "agnostic-lite"]
 tokio = ["dep:tokio", "futures-core", "pin-project-lite", "agnostic-lite/tokio"]
-smol = ["agnostic-lite/smol"]
-async-std = ["agnostic-lite/async-std"]
+smol = ["agnostic-lite/smol", "future"]
+async-std = ["agnostic-lite/async-std", "future"]
 
 [dependencies]
 parking_lot = { version = "0.12", optional = true }