Cargo Features
Btl has no features set by default.
[dependencies]
btl = { version = "0.3.0", features = ["tokio_shell"] }- tokio_shell = 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.
set tokio as the only optional dependency needed for the asynchronous version of the shell