Cargo Features

GPX has no features set by default.

[dependencies]
gpx = { version = "0.10.0", features = ["use-serde"] }
use-serde = serde

Enables serde of geo-types and time

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.

serde use-serde?