Cargo Features

unicom has no features set by default.

unicom = { version = "0.4.0", features = ["async", "rustdoc"] }
async = futures-io
rustdoc = 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.

futures-io async?
tokio rustdoc?