diff --git a/lib/domain/dart_rss.dart b/lib/domain/dart_rss.dart
index 9017a27..5e5531a 100644
--- a/lib/domain/dart_rss.dart
+++ b/lib/domain/dart_rss.dart
@@ -1,8 +1,6 @@
 import 'package:dart_rss/dart_rss.dart';
 import 'package:http/http.dart' as http;
-import 'package:dart_rss/domain/atom_feed.dart';
 import 'package:dart_rss/domain/rss1_feed.dart';
-import 'package:dart_rss/domain/rss_feed.dart';
 import 'package:xml/xml.dart' as xml;
 import 'package:intl/intl.dart';
 
@@ -142,7 +140,7 @@ class WebFeed {
         : rssRefs.first.getAttribute('version')?.contains('2');
     xmlns = feedRefs.isEmpty
         ? false
-        : feedRefs.first.getAttribute('xmlns')?.toLowerCase()?.contains('atom');
+        : feedRefs.first.getAttribute('xmlns')?.toLowerCase().contains('atom');
 
     if (rdfRefs.isNotEmpty) {
       return RssVersion.RSS1;
diff --git a/lib/domain/media/media.dart b/lib/domain/media/media.dart
index f108493..c8f8f4c 100644
--- a/lib/domain/media/media.dart
+++ b/lib/domain/media/media.dart
@@ -107,19 +107,19 @@ class Media {
       community: Community.parse(findElementOrNull(element, 'media:community')),
       comments: findElementOrNull(element, 'media:comments')
               ?.findElements('media:comment')
-              ?.map((e) => e.text)
-              ?.toList() ??
+              .map((e) => e.text)
+              .toList() ??
           <String>[],
       embed: Embed.parse(findElementOrNull(element, 'media:embed')),
       responses: findElementOrNull(element, 'media:responses')
               ?.findElements('media:response')
-              ?.map((e) => e.text)
-              ?.toList() ??
+              .map((e) => e.text)
+              .toList() ??
           <String>[],
       backLinks: findElementOrNull(element, 'media:backLinks')
               ?.findElements('media:backLink')
-              ?.map((e) => e.text)
-              ?.toList() ??
+              .map((e) => e.text)
+              .toList() ??
           <String>[],
       status: Status.parse(findElementOrNull(element, 'media:status')),
       prices: element
@@ -131,8 +131,8 @@ class Media {
       rights: Rights.parse(findElementOrNull(element, 'media:rights')),
       scenes: findElementOrNull(element, 'media:scenes')
               ?.findElements('media:scene')
-              ?.map((e) => Scene.parse(e))
-              ?.toList() ??
+              .map((e) => Scene.parse(e))
+              .toList() ??
           <Scene>[],
     );
   }
diff --git a/lib/domain/rss_item_itunes.dart b/lib/domain/rss_item_itunes.dart
index 89e5def..dc7dc57 100644
--- a/lib/domain/rss_item_itunes.dart
+++ b/lib/domain/rss_item_itunes.dart
@@ -37,26 +37,28 @@ class RssItemItunes {
   });
 
   factory RssItemItunes.parse(XmlElement element) {
-    final episodeStr = findElementOrNull(element, 'itunes:episode')?.text?.trim();
-    final seasonStr = findElementOrNull(element, 'itunes:season')?.text?.trim();
-    final durationStr = findElementOrNull(element, 'itunes:duration')?.text?.trim();
+    final episodeStr =
+        findElementOrNull(element, 'itunes:episode')?.text.trim();
+    final seasonStr = findElementOrNull(element, 'itunes:season')?.text.trim();
+    final durationStr =
+        findElementOrNull(element, 'itunes:duration')?.text.trim();
 
     return RssItemItunes(
-      title: findElementOrNull(element, 'itunes:title')?.text?.trim(),
+      title: findElementOrNull(element, 'itunes:title')?.text.trim(),
       episode: episodeStr == null ? null : int.tryParse(episodeStr),
       season: seasonStr == null ? null : int.tryParse(seasonStr),
       duration: durationStr == null ? null : parseDuration(durationStr),
       episodeType: newRssItunesEpisodeType(
           findElementOrNull(element, 'itunes:episodeType')),
-      author: findElementOrNull(element, 'itunes:author')?.text?.trim(),
-      summary: findElementOrNull(element, 'itunes:summary')?.text?.trim(),
+      author: findElementOrNull(element, 'itunes:author')?.text.trim(),
+      summary: findElementOrNull(element, 'itunes:summary')?.text.trim(),
       explicit: parseBoolLiteral(element, 'itunes:explicit'),
-      subtitle: findElementOrNull(element, 'itunes:subtitle')?.text?.trim(),
+      subtitle: findElementOrNull(element, 'itunes:subtitle')?.text.trim(),
       keywords: findElementOrNull(element, 'itunes:keywords')
               ?.text
-              ?.split(',')
-              ?.map((keyword) => keyword.trim())
-              ?.toList() ??
+              .split(',')
+              .map((keyword) => keyword.trim())
+              .toList() ??
           const <String>[],
       image: RssItunesImage.parse(findElementOrNull(element, 'itunes:image')),
       category: RssItunesCategory.parse(
diff --git a/lib/domain/rss_itunes.dart b/lib/domain/rss_itunes.dart
index e21aded..1b7028a 100644
--- a/lib/domain/rss_itunes.dart
+++ b/lib/domain/rss_itunes.dart
@@ -41,17 +41,17 @@ class RssItunes {
   factory RssItunes.parse(XmlElement element) {
     final categories = findAllDirectElementsOrNull(element, 'itunes:category');
     return RssItunes(
-      author: findElementOrNull(element, 'itunes:author')?.text?.trim(),
-      summary: findElementOrNull(element, 'itunes:summary')?.text?.trim(),
+      author: findElementOrNull(element, 'itunes:author')?.text.trim(),
+      summary: findElementOrNull(element, 'itunes:summary')?.text.trim(),
       explicit: parseBoolLiteral(element, 'itunes:explicit'),
-      title: findElementOrNull(element, 'itunes:title')?.text?.trim(),
-      subtitle: findElementOrNull(element, 'itunes:subtitle')?.text?.trim(),
+      title: findElementOrNull(element, 'itunes:title')?.text.trim(),
+      subtitle: findElementOrNull(element, 'itunes:subtitle')?.text.trim(),
       owner: RssItunesOwner.parse(findElementOrNull(element, 'itunes:owner')),
       keywords: findElementOrNull(element, 'itunes:keywords')
               ?.text
-              ?.split(',')
-              ?.map((keyword) => keyword.trim())
-              ?.toList() ??
+              .split(',')
+              .map((keyword) => keyword.trim())
+              .toList() ??
           const <String>[],
       image: RssItunesImage.parse(findElementOrNull(element, 'itunes:image')),
       categories:
@@ -59,10 +59,9 @@ class RssItunes {
               const <RssItunesCategory>[],
       type: newRssItunesType(findElementOrNull(element, 'itunes:type')),
       newFeedUrl:
-          findElementOrNull(element, 'itunes:new-feed-url')?.text?.trim(),
+          findElementOrNull(element, 'itunes:new-feed-url')?.text.trim(),
       block: parseBoolLiteral(element, 'itunes:block'),
       complete: parseBoolLiteral(element, 'itunes:complete'),
     );
   }
 }
-
diff --git a/lib/domain/rss_itunes_category.dart b/lib/domain/rss_itunes_category.dart
index df39050..402027c 100644
--- a/lib/domain/rss_itunes_category.dart
+++ b/lib/domain/rss_itunes_category.dart
@@ -22,7 +22,7 @@ class RssItunesCategory {
       category: element.getAttribute('text')?.trim(),
       subCategories: subCategories
               ?.map((ele) => ele.getAttribute('text')?.trim())
-              ?.toList() ??
+              .toList() ??
           <String>[],
     );
   }
diff --git a/lib/domain/rss_itunes_owner.dart b/lib/domain/rss_itunes_owner.dart
index 72e2d69..367cb3e 100644
--- a/lib/domain/rss_itunes_owner.dart
+++ b/lib/domain/rss_itunes_owner.dart
@@ -11,8 +11,8 @@ class RssItunesOwner {
   static RssItunesOwner? parse(XmlElement? element) {
     if (element == null) return null;
     return RssItunesOwner(
-      name: findElementOrNull(element, 'itunes:name')?.text?.trim(),
-      email: findElementOrNull(element, 'itunes:email')?.text?.trim(),
+      name: findElementOrNull(element, 'itunes:name')?.text.trim(),
+      email: findElementOrNull(element, 'itunes:email')?.text.trim(),
     );
   }
 }
diff --git a/lib/util/helpers.dart b/lib/util/helpers.dart
index 2982959..f567595 100644
--- a/lib/util/helpers.dart
+++ b/lib/util/helpers.dart
@@ -21,7 +21,7 @@ List<XmlElement>? findAllDirectElementsOrNull(XmlElement element, String name,
 }
 
 bool? parseBoolLiteral(XmlElement element, String tagName) {
-  final v = findElementOrNull(element, tagName)?.text?.toLowerCase()?.trim();
+  final v = findElementOrNull(element, tagName)?.text.toLowerCase().trim();
   if (v == null) return null;
   return ['yes', 'true'].contains(v);
 }
diff --git a/pubspec.yaml b/pubspec.yaml
index 70808d3..3ef744e 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,9 +1,9 @@
 name: dart_rss
-version: 2.0.1
+version: 3.0.0
 description: dart-rss is a rss parser for RSS1.0/RSS2.0/Atom. It also support Dublin-Core, Content, Syndication additional modules. This libary is forked from webfeed(https://github.com/witochandra/webfeed).
 homepage: https://github.com/sudame/dart-rss
 environment:
-  sdk: ">=2.12.0-259.9.beta <3.0.0"
+  sdk: ">=3.0.0 <4.0.0"
 dependencies:
   xml: ^5.0.2
   http: ^0.13.0
@@ -12,4 +12,3 @@ dependencies:
 dev_dependencies:
   test: ^1.16.4
   pedantic: ^1.10.0
-
diff --git a/test/atom_test.dart b/test/atom_test.dart
index 6bdd203..87610d4 100644
--- a/test/atom_test.dart
+++ b/test/atom_test.dart
@@ -11,7 +11,9 @@ void main() {
     try {
       AtomFeed.parse(xmlString);
       fail('Should throw Argument Error');
-    } on ArgumentError {}
+    } on ArgumentError {
+      // do nothing
+    }
   });
 
   test('parse Atom.xml', () {
diff --git a/test/rss_test.dart b/test/rss_test.dart
index 648416a..34b5e03 100644
--- a/test/rss_test.dart
+++ b/test/rss_test.dart
@@ -13,7 +13,9 @@ void main() {
     try {
       RssFeed.parse(xmlString);
       fail('Should throw Argument Error');
-    } on ArgumentError {}
+    } on ArgumentError {
+      // do nothing
+    }
   });
   test('parse RSS.xml', () {
     final xmlString = File('test/xml/RSS.xml').readAsStringSync();
@@ -350,10 +352,10 @@ void main() {
     expect(item.itunes!.title, 'awesome title');
     expect(item.itunes!.block, false);
   });
-  test("parse RSS-PodcastIndex-R1.xml", () {
-    var xmlString = new File("test/xml/RSS-PodcastIndex-R1.xml").readAsStringSync();
+  test('parse RSS-PodcastIndex-R1.xml', () {
+    var xmlString = File('test/xml/RSS-PodcastIndex-R1.xml').readAsStringSync();
 
-    var feed = new RssFeed.parse(xmlString);
+    var feed = RssFeed.parse(xmlString);
 
     expect(feed.title, 'Podcasting 2.0 Namespace Example');
     expect(