Cargo Features

futures-util-io-peek has no features set by default.

futures-util-io-peek = { version = "0.2.0", features = ["async_io_async", "tokio_tcp_stream"] }
async_io_async = async-io
tokio_tcp_stream = 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.

async-io async_io_async?

Enables async-io ^1

tokio tokio_tcp_stream?