my changes

app/Providers/SolariumServiceProvider.php

@@ -0,0 +1,43 @@
+<?php
+
+namespace App\Providers;
+
+use Illuminate\Support\ServiceProvider;
+use Solarium\Client;
+
+class SolariumServiceProvider extends ServiceProvider
+{
+    protected $defer = true;
+    
+
+    /**
+     * Register the application services.
+     *
+     * @return void
+     */
+    public function register()
+    {
+        $this->app->bind(Client::class, function ($app) {           
+            // $config = config('solarium');
+            $config = array(
+                    'endpoint' => array(
+                        'localhost' => array(
+                            'host' => '127.0.0.1', 
+                            'port' => '8983', 
+                            'path' => '/solr/',
+                            'core' => 'opus4'
+                        )
+                    )
+                );
+                //return new Client($config);
+                return new Client($config);
+                //return new Client($app['config']['solarium']);
+            });
+    }
+   
+    public function provides()
+    {
+        return [Client::class];
+    }
+
+}