MacOS App: How do we launch bundled helper program from main application?

I would like to achieve simple thing but struggling for the whole day. :(

I made a simple macOS app. In AppDelegate, applicationDidFinishLaunching, I would like to execute a helper program which is bundled together inside the app.

https://github.com/hkjlee109/objc-helper-example

But I am getting an error.

Load failed: 5: Input/output error
Try running `launchctl bootstrap` as root for richer errors.

Here's what I did: 0. From

1. I've a target called "helper-agent" which is a commandline application.
2. For "helper-agent" application, I've added "com.example.helper.agent.plist" file.

<?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>Label</key>
    <string>com.example.helper.agent</string>
    <key>BundleProgram</key>
    <string>Contents/Resources/helper-agent</string>
    <key>MachServices</key>
    <dict>
        <key>com.example.helper.agent</key>
        <true/>
    </dict>
</dict>
</plist>

And I've added two things for "Build phase" of main application.

1. Copy Bundle Resources: Copy "helper-agent" application to "Contents/Library/LaunchAgents"
2. Copy Files: Copy "com.example.helper.agent.plist" to "Contents/Library/LaunchAgents"

Lastly, in AppDelegate, I am using below code to launch the helper.

    NSTask* task = [NSTask new];
    task.launchPath = @"/bin/launchctl";
    task.arguments = @[@"load", @"com.example.helper.agent.plist"];
    [task launch];
    [task waitUntilExit];

I would be appreciated for any piece of advices or suggestions. Thanks!

https://github.com/hkjlee109/objc-helper-example