Error while installing the package

[8brothers]

While installing this package it throws this error:

Error 1:

Generating optimized autoload files

Illuminate\Foundation\ComposerScripts::postAutoloadDump
@php artisan package:discover --ansi
PHP Warning: Module 'intl' already loaded in Unknown on line 0
PHP Fatal error: Access level to Shopper\Framework\Console\InstallCommand::complete() must be public (as in class Symfony\Component\Console\Command\Command) in /var/www/html/laravel-shopper/vendor/shopper/framework/src/Console/InstallCommand.php on line 105

In InstallCommand.php line 105:

Access level to Shopper\Framework\Console\InstallCommand::complete() must be public (as in class Symfony\Component\Console\Command\Command)

Script @php artisan package:discover --ansi handling the post-autoload-dump event returned with error code 255

Installation failed, reverting ./composer.json and ./composer.lock to their original content.

Please note that as per previous error I have update the complete method to public after the method is public it throws below error.

Error 2:

Generating optimized autoload files

Illuminate\Foundation\ComposerScripts::postAutoloadDump
@php artisan package:discover --ansi
PHP Warning: Module 'intl' already loaded in Unknown on line 0
PHP Fatal error: Declaration of Shopper\Framework\Console\InstallCommand::complete() must be compatible with Symfony\Component\Console\Command\Command::complete(Symfony\Component\Console\Completion\CompletionInput $input, Symfony\Component\Console\Completion\CompletionSuggestions $suggestions): void in /var/www/html/laravel-shopper/vendor/shopper/framework/src/Console/InstallCommand.php on line 105

In InstallCommand.php line 105:

Declaration of Shopper\Framework\Console\InstallCommand::complete() must be compatible with Symfony\Component\Console\Command\Command::complete(Symfony\Component\Console\Completion\CompletionInput $
input, Symfony\Component\Console\Completion\CompletionSuggestions $suggestions): void

Script @php artisan package:discover --ansi handling the post-autoload-dump event returned with error code 255

Installation failed, reverting ./composer.json and ./composer.lock to their original content.

[detygon]

Hey, a stable version has just been released. You should check it out.