Handshake error on flutter with Laravel 7

I use Laravel 7 for backend, Nginx on the server, and flutter for apps.

I installed an SSL layer for my server by using Let's encrypt and Certbot. Before SSL everything was fine, it was working. But after installing SSL I got this error on flutter:

HandshakeExceiption: Handshake error in client (OS error: TLSV1_ALERT_PROTOCOL_VERSION(tls_record.cc:587))

It is my flutter request code:

import 'package:package_info/package_info.dart';
import 'dart:io';
import 'package:dio/dio.dart';
import './home.dart';
import './auth.dart';

String token;

class RootProvider {
  static Dio http = Dio();
  static final baseUrl = "https://my_domain.com/api";
  static String locale = '';

  static Future<void> setRequestHeaders() async {
    token = await AuthProvider.getToken();
    String _locale = await HomeProvider.getLocale();
    locale = _locale == 'en' ? 'tm' : _locale;
    PackageInfo packageInfo = await PackageInfo.fromPlatform();
    String platform = "";

    if (Platform.isAndroid) {
      platform = "android";
    } else if (Platform.isIOS) {
      platform = "ios";
    }

    var headers = {
      'Accept': 'application/json',
      'Content-Type': 'application/json',
      'Language': _locale == 'en' ? 'tm' : _locale,
      'Version': packageInfo?.version,
      'Platform': platform,
    };
    if (token != null) headers['Authorization'] = "Bearer $token";
    http.options.baseUrl = baseUrl;
    http.options.headers = headers;
  }

  static init() async {
    await setRequestHeaders();

    http.interceptors.add(
      InterceptorsWrapper(
        onRequest: (RequestOptions options) {
          print('Making request to ${options.method} ${options.uri}');
        },
        onResponse: (Response response) {
          // if response successful then return data
          if (response.data['success'] == true && response.data['success']) {
            return http.resolve(response);
          }

          return http.reject(response.data['message']);
        },
        onError: (DioError e) async {
          return http.reject(e);
        },
      ),
    );
  }
}

It is my Nginx conf:

server {
    listen 80;
    listen [::]:80;

    server_name my_domain.com;
    return 301 https://$server_name$request_uri;
}

server {
    listen 443 ssl http2;
    listen [::]:443 ssl http2;
    server_name my_domain.com;
    root /var/www/my_domain/public;

        ssl_certificate /etc/letsencrypt/live/my_domain.com/fullchain.pem;
        ssl_certificate_key /etc/letsencrypt/live/my_domain.com/privkey.pem;

        include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
        ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

        add_header X-Frame-Options "SAMEORIGIN";
        add_header X-XSS-Protection "1; mode=block";
        add_header X-Content-Type-Options "nosniff";

        index index.php index.html index.htm index.nginx-debian.html;

    charset utf-8;

    location / {
            try_files $uri $uri/ /index.php?$query_string;
    }

    location ~ \.php$ {
        include snippets/fastcgi-php.conf;
        fastcgi_pass unix:/var/run/php/php7.4-fpm.sock;
    }

    location ~ /\.ht {
            deny all;
    }

    location ~ /.well-known {
            allow all;
    }
}

Note: I tried to send a request by Axios on javascript and I got a success response. It works on Axios and Javascript. It is only not working on flutter.

Please, help me to find problem. Thank you in advance