Enable alloc feature for the futures crate

Author: robertwayne

Cargo.toml

@@ -32,10 +32,12 @@ serde_json = { version = "1", optional = true }
 
 # Optional dependencies required for the `auto-vary` feature.
 tokio = { version = "1", features = ["sync"], optional = true }
-futures = { version = "0.3", default-features = false, optional = true }
+futures = { version = "0.3", default-features = false, features = [
+    "alloc",
+], optional = true }
 
 [dev-dependencies]
-axum = { version = "0.8", default-features = false}
+axum = { version = "0.8", default-features = false }
 axum-test = "17"
 tokio = { version = "1", features = ["full"] }
 tokio-test = "0.4"