ConnectToCorrectDatabase.php

<?php

namespace App\Http\Middleware;

use Closure;
use Config;

class ConnectToCorrectDatabase
{
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {
        $databaseSettings = Config::get('database.connections.mysql');

        $databaseSettings['username'] = 'test';

        Config::set("database.connections.mysql", $databaseSettings);

        return $next($request);
    }
}