Build

Set allow_null_fields to true in tracing options #515

	name: Build
	on: [push]
	jobs:
	build:
	name: Build for ${{ matrix.os }}
	runs-on: ${{ matrix.os }}
	strategy:
	matrix:
	# Building proj on Windows is a mess, so not enabled yet. https://github.com/georust/proj/pull/79
	build: [linux, macos]
	include:
	- build: linux
	os: ubuntu-latest
	- build: macos
	os: macos-latest

	steps:
	- uses: actions/checkout@master

	- uses: hecrj/setup-rust-action@v1
	with:
	rust-version: stable

	- name: Install protoc
	uses: arduino/setup-protoc@v1
	with:
	repo-token: ${{ secrets.GITHUB_TOKEN }}

	- name: Cache build
	uses: actions/cache@v2
	with:
	path: target
	# The key could include hashFiles('Cargo.lock'), but cargo will figure out what can be reused.
	key: build-${{ matrix.os }}

	- name: Build
	run: cargo check

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