Cargo Features

[dependencies]
nimble = { version = "0.2.1", default-features = false, features = ["futures", "derive", "tokio"] }
default = futures

The futures feature is set by default whenever nimble is added without default-features = false somewhere in the dependency tree.

futures default = futures-util
derive = nimble-derive

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-util futures
nimble-derive derive?
tokio implicit feature

Enables tokio ^0.2

tokio:

An event-driven, non-blocking I/O platform for writing asynchronous I/O backed applications