Getting error while dropping foreign key column in laravel

If  you get an error like this while running migrate refresh:

 SQLSTATE[HY000]: General error: 1005 Can't create table `blogname`.`#sql-6b44_1f1` (errno: 150 "Foreign key constraint is incorrectly formed") (SQL: alter table `blogs` add constraint `blogs_user_id_foreign` foreign key (`user_id`) references `users` (`id`) on delete cascade)

then go to your migration file and write the down() function like the following:

public function up()

    {

        Schema::table('blogs', function (Blueprint $table) {

            $table->bigInteger('user_id')->unsigned()->index()->nullable();

            $table->foreign('user_id')->references('id')->on('users')
->onDelete('cascade');

        });

    }

    /**

     * Reverse the migrations.

     *

     * @return void

     */

    public function down()

    {

        Schema::table('blogs', function (Blueprint $table) {

            $table->dropForeign(['user_id']);

$table->dropColumn('user_id');

        });

    }