aria2c daemon start at boot. Put this file into /Library/LaunchDaemons, them 'chmod 600' and 'chown root'. Remember to fill placeholders below.

homebrew.mxcl.aria2.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>KeepAlive</key>
	<true/>
	<key>RunAtLoad</key>
	<true/>
	<key>Label</key>
	<string>homebrew.mxcl.aria2</string>
	<key>ProgramArguments</key>
	<array>
		<string>/usr/local/bin/aria2c</string>
		<string>--enable-rpc=true</string>
		<string>--rpc-secret=<your secret></string>
		<string>--rpc-allow-origin-all=true</string>
		<string>--rpc-listen-all=true</string>
		<string>--rpc-listen-port=6800</string>
	</array>
	<key>WorkingDirectory</key>
	<string>/Users/<your username>/Downloads</string>
</dict>
</plist>

What label should be used if the installation isn't done via homebrew? Thank you very much!

Thank you very much this one works like charm!
BTW, if you are using Homebrew Aria2 instead of put this file into /Library/LaunchDaemons, you can put this file into /usr/local/Cellar/aria2/VERSION/ then you will be able to control it via brew services cmd.

this is great, i was looking for this

Thank you very much this one works like charm!
BTW, if you are using Homebrew Aria2 instead of put this file into /Library/LaunchDaemons, you can put this file into /usr/local/Cellar/aria2/VERSION/ then you will be able to control it via brew services cmd.