Cargo Features

gpio-cdev has no features set by default.

[dependencies]
gpio-cdev = { version = "0.6.0", features = ["async-tokio"] }
async-tokio = futures, tokio

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

tokio async-tokio?
futures async-tokio?