你可以使用 cargo-feature crate 来查看和管理你的依赖特性：
> cargo install cargo-feature --locked
> cargo feature postgres
Avaliable features for `postgres`
array-impls = ["tokio-postgres/array-impls"]
with-bit-vec-0_6 = ["tokio-postgres/with-bit-vec-0_6"]
with-chrono-0_4 = ["tokio-postgres/with-chrono-0_4"]
with-eui48-0_4 = ["tokio-postgres/with-eui48-0_4"]
with-eui48-1 = ["tokio-postgres/with-eui48-1"]
with-geo-types-0_6 = ["tokio-postgres/with-geo-types-0_6"]
with-geo-types-0_7 = ["tokio-postgres/with-geo-types-0_7"]
with-serde_json-1 = ["tokio-postgres/with-serde_json-1"]
with-smol_str-01 = ["tokio-postgres/with-smol_str-01"]
with-time-0_2 = ["tokio-postgres/with-time-0_2"]
with-time-0_3 = ["tokio-postgres/with-time-0_3"]
with-uuid-0_8 = ["tokio-postgres/with-uuid-0_8"]
with-uuid-1 = ["tokio-postgres/with-uuid-1"]
注意：只有在包已经作为依赖项存在于 Cargo.toml 中时，此方法才有效。
在使用 cargo add 命令时，还会显示功能列表：
> cargo add postgres
Updating crates.io index
Adding postgres v0.19.4 to dependencies.
Features:
- array-impls
- with-bit-vec-0_6
- with-chrono-0_4
- with-eui48-0_4
- with-eui48-1
- with-geo-types-0_6
- with-geo-types-0_7
- with-serde_json-1
- with-smol_str-01
- with-time-0_2
- with-time-0_3
- with-uuid-0_8
- with-uuid-1