app-api/app/Models/Wetalk/Comment.php

<?php

namespace App\Models\Wetalk;

use Illuminate\Database\Eloquent\Model;
use DateTimeInterface;
use App\Models\User;

class Comment extends Model
{
    protected $connection = 'mysql_t';
    protected $table='comment';
    protected $guarded=[];
    protected function serializeDate(DateTimeInterface $date): string
    {
        return $date->format('Y-m-d H:i:s');
    }

    public function user(){
//        $instance = new User;
//        $instance->setConnection('mysql');
//        $query = $instance->newQuery();
//        return $this->hasOne($query, $this,'id','user_id');

        return $this->hasOne('App\Models\User','id','user_id');
    }
}