Cargo Features

proj5 has no features set by default.

[dependencies]
proj5 = { version = "0.1.7", features = ["multithreading"] }
multithreading = scoped_threadpool

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.

scoped_threadpool multithreading?