laravel sync()同步时修改中间表字段

class User extends Model
{
    public function groups()
    {
      return $this->belongsToMany(Group::class)
     ->withPivot('expiration_time');
    }

    //修改中间表字段
    public function setGroup($group)
        {
            $this->groups()->sync([
                $group => [//$group是id
                'expiration_time' => \Illuminate\Support\Carbon::now()
                ]
            ]);

            return $this;
        }
}Copy