diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1ffc1a5..7db7f70 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## [0.2.0] - 22/09/2021
+
+* Upgrade package to Dart 2.12 and sound null safety.
+
 ## [0.1.0] - 22/02/2020
 
 * Bump up version, API is quite stable and we use the package successfully in production.
diff --git a/packages/span_builder/CHANGELOG.md b/packages/span_builder/CHANGELOG.md
index 1ffc1a5..7db7f70 100644
--- a/packages/span_builder/CHANGELOG.md
+++ b/packages/span_builder/CHANGELOG.md
@@ -1,3 +1,7 @@
+## [0.2.0] - 22/09/2021
+
+* Upgrade package to Dart 2.12 and sound null safety.
+
 ## [0.1.0] - 22/02/2020
 
 * Bump up version, API is quite stable and we use the package successfully in production.
diff --git a/packages/span_builder/example/lib/main.dart b/packages/span_builder/example/lib/main.dart
index 09a0438..59b46b5 100644
--- a/packages/span_builder/example/lib/main.dart
+++ b/packages/span_builder/example/lib/main.dart
@@ -33,12 +33,12 @@ class MyApp extends StatelessWidget {
                                   style: TextStyle(
                                       decoration: TextDecoration.underline)),
                               onTap: () {
-                            Scaffold.of(context).showSnackBar(
+                            ScaffoldMessenger.of(context).showSnackBar(
                                 const SnackBar(content: Text("weeeee")));
                           })
                           ..apply(const TextSpan(text: "🐶"), whereText: "dog"),
                         defaultStyle:
-                            TextStyle(color: Colors.black, fontSize: 32.0),
+                            const TextStyle(color: Colors.black, fontSize: 32.0),
                         textAlign: TextAlign.center)))));
   }
 }
diff --git a/packages/span_builder/example/pubspec.lock b/packages/span_builder/example/pubspec.lock
index e0e29f6..045c198 100644
--- a/packages/span_builder/example/pubspec.lock
+++ b/packages/span_builder/example/pubspec.lock
@@ -1,62 +1,48 @@
 # Generated by pub
 # See https://dart.dev/tools/pub/glossary#lockfile
 packages:
-  archive:
-    dependency: transitive
-    description:
-      name: archive
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.11"
-  args:
-    dependency: transitive
-    description:
-      name: args
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.5.2"
   async:
     dependency: transitive
     description:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.4.0"
+    version: "2.8.1"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.5"
-  charcode:
+    version: "2.1.0"
+  characters:
     dependency: transitive
     description:
-      name: charcode
+      name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.2"
-  collection:
+    version: "1.1.0"
+  charcode:
     dependency: transitive
     description:
-      name: collection
+      name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.11"
-  convert:
+    version: "1.3.1"
+  clock:
     dependency: transitive
     description:
-      name: convert
+      name: clock
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.1"
-  crypto:
+    version: "1.1.0"
+  collection:
     dependency: transitive
     description:
-      name: crypto
+      name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.3"
+    version: "1.15.0"
   cupertino_icons:
     dependency: "direct main"
     description:
@@ -64,6 +50,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "0.1.3"
+  fake_async:
+    dependency: transitive
+    description:
+      name: fake_async
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.2.0"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -74,55 +67,27 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
-  image:
-    dependency: transitive
-    description:
-      name: image
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.1.4"
   matcher:
     dependency: transitive
     description:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.6"
+    version: "0.12.10"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.8"
+    version: "1.7.0"
   path:
     dependency: transitive
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.6.4"
-  pedantic:
-    dependency: transitive
-    description:
-      name: pedantic
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.8.0+1"
-  petitparser:
-    dependency: transitive
-    description:
-      name: petitparser
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.4.0"
-  quiver:
-    dependency: transitive
-    description:
-      name: quiver
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.5"
+    version: "1.8.0"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -134,76 +99,69 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.5.5"
+    version: "1.8.1"
   span_builder:
     dependency: "direct main"
     description:
       path: ".."
       relative: true
     source: path
-    version: "0.0.1"
+    version: "0.2.0"
   span_builder_test:
     dependency: "direct dev"
     description:
       path: "../../span_builder_test"
       relative: true
     source: path
-    version: "0.0.1"
+    version: "0.2.0"
   stack_trace:
     dependency: transitive
     description:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.3"
+    version: "1.10.0"
   stream_channel:
     dependency: transitive
     description:
       name: stream_channel
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.1.0"
   string_scanner:
     dependency: transitive
     description:
       name: string_scanner
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.5"
+    version: "1.1.0"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
+    version: "1.2.0"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.11"
+    version: "0.4.2"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.6"
+    version: "1.3.0"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.8"
-  xml:
-    dependency: transitive
-    description:
-      name: xml
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "3.5.0"
+    version: "2.1.0"
 sdks:
-  dart: ">=2.6.0 <3.0.0"
+  dart: ">=2.12.0 <3.0.0"
diff --git a/packages/span_builder/example/pubspec.yaml b/packages/span_builder/example/pubspec.yaml
index d40d716..042ac95 100644
--- a/packages/span_builder/example/pubspec.yaml
+++ b/packages/span_builder/example/pubspec.yaml
@@ -4,7 +4,7 @@ description: Example app for span_builder
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.1.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   flutter:
diff --git a/packages/span_builder/example/test/widget_test.dart b/packages/span_builder/example/test/widget_test.dart
index 6f2e1a3..867082b 100644
--- a/packages/span_builder/example/test/widget_test.dart
+++ b/packages/span_builder/example/test/widget_test.dart
@@ -10,12 +10,12 @@ void main() {
     final spanFinder = find.byKey(span_key);
 
     expect(spanFinder, findsOneWidget);
-    final allSpans = tester.findSpans(spanFinder).length;
+    final allSpans = tester.findSpans(spanFinder)?.length;
     expect(allSpans, 8);
 
     final foxSpans = tester.findSpans(spanFinder, predicate: (span) {
       return span is TextSpan && span.text == "🦊";
     });
-    expect(foxSpans.length, 1);
+    expect(foxSpans?.length, 1);
   });
 }
diff --git a/packages/span_builder/lib/src/span_builder.dart b/packages/span_builder/lib/src/span_builder.dart
index af3db2c..37191b2 100644
--- a/packages/span_builder/lib/src/span_builder.dart
+++ b/packages/span_builder/lib/src/span_builder.dart
@@ -4,7 +4,7 @@ import 'package:flutter/widgets.dart';
 /// represents position of a span in some plain text
 class SpanEntity {
   const SpanEntity(
-      {@required this.start, @required this.end, @required this.span})
+      {required this.start, required this.end, required this.span})
       : assert(start >= 0),
 
         /// we only accept _ManagedTextSpans since we must take care of managing the recognizer
@@ -26,12 +26,12 @@ class SpanEntity {
 }
 
 extension ManagedTextSpanExtension on TextSpan {
-  InlineSpan managed([RecognizerBuilder recognizerBuilder]) =>
+  InlineSpan managed([RecognizerBuilder? recognizerBuilder]) =>
       _ManagedTextSpan.fromTextSpan(this, recognizerBuilder: recognizerBuilder);
 }
 
 typedef RecognizerBuilder = GestureRecognizer Function();
-typedef _RecognizerBuilder = GestureRecognizer Function(_ManagedTextSpan);
+typedef _RecognizerBuilder = GestureRecognizer? Function(_ManagedTextSpan);
 
 /// Due to some [poor design choices](https://github.com/flutter/flutter/issues/10623#issuecomment-345790443)
 /// you need to dispose [TextSpan]'s [GestureRecognizer] yourself. When you are formatting text, thinking about
@@ -41,20 +41,20 @@ typedef _RecognizerBuilder = GestureRecognizer Function(_ManagedTextSpan);
 class _ManagedTextSpan extends TextSpan {
   const _ManagedTextSpan({
     this.recognizerBuilder,
-    String text,
-    TextStyle style,
-    String semanticsLabel,
+    String? text,
+    TextStyle? style,
+    String? semanticsLabel,
   }) : super(text: text, style: style, semanticsLabel: semanticsLabel);
   _ManagedTextSpan.fromTextSpan(TextSpan textSpan,
-      {RecognizerBuilder recognizerBuilder})
+      {RecognizerBuilder? recognizerBuilder})
       : this(
             text: textSpan.text,
             style: textSpan.style,
             semanticsLabel: textSpan.semanticsLabel,
             recognizerBuilder: recognizerBuilder);
-  final RecognizerBuilder recognizerBuilder;
+  final RecognizerBuilder? recognizerBuilder;
 
-  TextSpan withManagedRecognizer(GestureRecognizer managedRecognizer) {
+  TextSpan withManagedRecognizer(GestureRecognizer? managedRecognizer) {
     return TextSpan(
         style: style,
         text: text,
@@ -85,11 +85,11 @@ class SpanBuilder {
   final _entities = <SpanEntity>[];
 
   SpanBuilder apply(InlineSpan span,
-      {String whereText,
-      int from,
-      int to,
-      Function() onTap,
-      RecognizerBuilder recognizerBuilder}) {
+      {String? whereText,
+      int? from,
+      int? to,
+      Function()? onTap,
+      RecognizerBuilder? recognizerBuilder}) {
     /// turn any [onTap] into [RecognizerBuilder]
     if (onTap != null && recognizerBuilder == null) {
       recognizerBuilder = () => TapGestureRecognizer()..onTap = onTap;
@@ -98,7 +98,7 @@ class SpanBuilder {
     /// convert [TextSpan] into [_ManagedTextSpan] with a [RecoginzerBuilder]
     if (span is TextSpan) {
       /// ignore: avoid_as
-      span = (span as TextSpan).managed(recognizerBuilder);
+      span = span.managed(recognizerBuilder);
     }
 
     /// if [whereText] is not provided then we try to figure it out:
@@ -134,7 +134,7 @@ class SpanBuilder {
     }
 
     /// finally we appen calculated SpanPosition
-    return add(SpanEntity(start: offset + from, end: offset + to, span: span));
+    return add(SpanEntity(start: offset + from!, end: offset + to!, span: span));
   }
 
   /// we sort entities when we add them, if any of the entities is overlapping,
@@ -155,7 +155,7 @@ class SpanBuilder {
     return this;
   }
 
-  List<InlineSpan> build({_RecognizerBuilder recognizerBuilder}) =>
+  List<InlineSpan> build({_RecognizerBuilder? recognizerBuilder}) =>
       _computeSpans(sourceText, _entities, recognizerBuilder);
 }
 
@@ -163,8 +163,8 @@ class SpanBuilder {
 /// disposing any related instances of [GestureRecognizer] that might be used in your text.
 class SpanBuilderWidget extends StatefulWidget {
   const SpanBuilderWidget(
-      {Key key,
-      @required this.text,
+      {Key? key,
+      required this.text,
       this.defaultStyle,
       this.textAlign = TextAlign.start,
       this.textDirection,
@@ -177,7 +177,7 @@ class SpanBuilderWidget extends StatefulWidget {
       this.textWidthBasis = TextWidthBasis.parent})
       : super(key: key);
   final SpanBuilder text;
-  final TextStyle defaultStyle;
+  final TextStyle? defaultStyle;
 
   @override
   State<StatefulWidget> createState() => _SpanBuilderWidgetState();
@@ -187,21 +187,21 @@ class SpanBuilderWidget extends StatefulWidget {
 
   /// wrapping [RichText] fields
   final TextAlign textAlign;
-  final TextDirection textDirection;
+  final TextDirection? textDirection;
   final bool softWrap;
   final TextOverflow overflow;
   final double textScaleFactor;
-  final int maxLines;
-  final Locale locale;
-  final StrutStyle strutStyle;
+  final int? maxLines;
+  final Locale? locale;
+  final StrutStyle? strutStyle;
   final TextWidthBasis textWidthBasis;
 }
 
 class _SpanBuilderWidgetState extends State<SpanBuilderWidget> {
-  TextSpan _textSpan;
+  late TextSpan _textSpan;
   final _recongnizers = <GestureRecognizer>[];
 
-  GestureRecognizer recognizerBuilder(_ManagedTextSpan textSpan) {
+  GestureRecognizer? recognizerBuilder(_ManagedTextSpan textSpan) {
     final recognizer = textSpan.recognizerBuilder?.call();
     if (recognizer != null) {
       if (SpanBuilderWidget.debugPrint) {
@@ -268,7 +268,7 @@ class _SpanBuilderWidgetState extends State<SpanBuilderWidget> {
 
 /// CONTRACT: entities must come sorted by their appearance and should not overlap
 List<InlineSpan> _computeSpans(String text, List<SpanEntity> entities,
-    _RecognizerBuilder recognizerBuilder) {
+    _RecognizerBuilder? recognizerBuilder) {
   final output = <InlineSpan>[];
   var currentIndex = 0;
   for (final entity in entities) {
diff --git a/packages/span_builder/pubspec.yaml b/packages/span_builder/pubspec.yaml
index 5d5f745..03751ff 100644
--- a/packages/span_builder/pubspec.yaml
+++ b/packages/span_builder/pubspec.yaml
@@ -1,10 +1,10 @@
 name: span_builder
 description: Facilitates creation of spans from plain text and provides automated disposal of GestureRecognizers
-version: 0.1.0
+version: 0.2.0
 homepage: https://github.com/eyeem/span_builder
 
 environment:
-  sdk: ">=2.6.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   flutter:
diff --git a/packages/span_builder/test/span_builder_test.dart b/packages/span_builder/test/span_builder_test.dart
index beeb990..d4a7631 100644
--- a/packages/span_builder/test/span_builder_test.dart
+++ b/packages/span_builder/test/span_builder_test.dart
@@ -42,12 +42,12 @@ void main() {
     expect(tapped, isFalse);
 
     final textWidget = tester.widget<RichText>(find.byType(RichText));
-    final TextSpan span = textWidget.text;
-    final spans = span.children;
+    final span = textWidget.text as TextSpan;
+    final spans = span.children!;
     expect(spans, hasLength(4));
 
     // fake tap
-    ((spans[1] as TextSpan).recognizer as TapGestureRecognizer).onTap();
+    ((spans[1] as TextSpan).recognizer as TapGestureRecognizer).onTap!();
 
     expect(tapped, isTrue);
   });
diff --git a/packages/span_builder_test/CHANGELOG.md b/packages/span_builder_test/CHANGELOG.md
index 1ffc1a5..7db7f70 100644
--- a/packages/span_builder_test/CHANGELOG.md
+++ b/packages/span_builder_test/CHANGELOG.md
@@ -1,3 +1,7 @@
+## [0.2.0] - 22/09/2021
+
+* Upgrade package to Dart 2.12 and sound null safety.
+
 ## [0.1.0] - 22/02/2020
 
 * Bump up version, API is quite stable and we use the package successfully in production.
diff --git a/packages/span_builder_test/lib/src/span_builder_test.dart b/packages/span_builder_test/lib/src/span_builder_test.dart
index 8a61a88..11b5563 100644
--- a/packages/span_builder_test/lib/src/span_builder_test.dart
+++ b/packages/span_builder_test/lib/src/span_builder_test.dart
@@ -5,15 +5,15 @@ import 'package:flutter_test/flutter_test.dart';
 /// https://github.com/flutter/flutter/blob/master/packages/flutter/test/widgets/hyperlink_test.dart#L47
 /// sooo...
 extension WidgetTesterRichEditExtension on WidgetTester {
-  Iterable<InlineSpan> findSpans(Finder spanWidgetFinder,
-      {bool Function(InlineSpan) predicate}) {
+  Iterable<InlineSpan>? findSpans(Finder spanWidgetFinder,
+      {bool Function(InlineSpan)? predicate}) {
     final richTextFinder =
         find.descendant(of: spanWidgetFinder, matching: find.byType(RichText));
     final richText = widget<RichText>(richTextFinder);
     expect(richText.text, isInstanceOf<TextSpan>());
-    final TextSpan innerText = richText.text;
+    final innerText = richText.text as TextSpan;
     return predicate == null
         ? innerText.children
-        : innerText.children.where(predicate);
+        : innerText.children?.where(predicate);
   }
 }
diff --git a/packages/span_builder_test/pubspec.yaml b/packages/span_builder_test/pubspec.yaml
index 91a8dd9..8f03212 100644
--- a/packages/span_builder_test/pubspec.yaml
+++ b/packages/span_builder_test/pubspec.yaml
@@ -1,10 +1,10 @@
 name: span_builder_test
 description: WidgetTester helpers and extensions for testing span_builder
-version: 0.1.0
+version: 0.2.0
 homepage: https://github.com/eyeem/span_builder_test
 
 environment:
-  sdk: ">=2.6.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   flutter: