diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 57c57f8..e1c24fe 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -60,15 +60,11 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: actions-rust-lang/setup-rust-toolchain@v1
-      - uses: actions-rs/cargo@v1
         with:
-          command: install
-          args: cargo-all-features
-      - uses: actions-rs/cargo@v1
-        with:
-          command: build-all-features
-          args: -F ${{ matrix.channel }} --all-targets
-      - uses: actions-rs/cargo@v1
-        with:
-          command: test-all-features
-          args: -F ${{ matrix.channel }} --lib
+          toolchain: ${{ matrix.toolchain }}
+      - name: Install cargo-all-features
+        run: cargo install cargo-all-features
+      - name: Build all feature combinations
+        run: cargo build-all-features -- -F ${{ matrix.channel }} --all-targets
+      - name: Test all feature combinations
+        run: cargo test-all-features -- -F ${{ matrix.channel }} --lib
diff --git a/.gitignore b/.gitignore
index 6959e18..8e8abb0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -25,3 +25,4 @@ Cargo.lock
 /target
 
 lcov.info
+.omc/
diff --git a/Cargo.toml b/Cargo.toml
index 56119a5..f7a2149 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -31,6 +31,8 @@ core_affinity = { version = "0.8.1", optional = true }
 # functionality of these crates internally (other than in tests)
 flume = { version = "0.11.1", optional = true }
 loole = { version = "0.4.0", optional = true }
+# required with the `async` feature
+tokio = { version = "1", optional = true }
 
 [dev-dependencies]
 divan = "0.1.17"
@@ -48,6 +50,7 @@ harness = false
 [features]
 default = ["local-batch"]
 affinity = ["dep:core_affinity"]
+async = ["tokio"]
 local-batch = []
 retry = []
 crossbeam = []
diff --git a/src/hive/inner/shared.rs b/src/hive/inner/shared.rs
index dc9728d..0d0f415 100644
--- a/src/hive/inner/shared.rs
+++ b/src/hive/inner/shared.rs
@@ -143,7 +143,7 @@ impl<W: Worker, Q: Queen<Kind = W>, T: TaskQueues<Q::Kind>> Shared<Q, T> {
     }
 
     /// Returns the mutex guard for the results of spawing worker threads.
-    pub fn spawn_results(&self) -> MutexGuard<Vec<Result<JoinHandle<()>, SpawnError>>> {
+    pub fn spawn_results(&self) -> MutexGuard<'_, Vec<Result<JoinHandle<()>, SpawnError>>> {
         self.spawn_results.lock()
     }