[ARROW-3960] [Rust] remove extern crate for Rust 2018

• Type: Improvement
• Status: Resolved
• Priority: Trivial
• Resolution: Fixed
• Fix Version/s: 0.12.0
• Component/s: Rust
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/20564
• Assignee: Chao Sun
• Reporter: Chao Sun
• Created: 08/Dec/18 07:30
• Updated: 11/Jan/23 07:30
• Resolved: 12/Dec/18 00:21

Description

This is a trivial change to remove "extern crate" definitions in lib.rs, by following new format in Rust 2018.

Issue Links

• is related to: ARROW-3952 [Rust] Specify edition="2018" in Cargo.toml
• links to: GitHub Pull Request #3125