Here you’ll find guided examples to get yourself familiarized with Gio.
Beginners
If you are unsure where to start, then this is a pretty good place:
Writing an hello world.
Jon Strand's tutorialImplementing an egg timer.
Example ProjectsDifferent examples of Gio features.
Common ErrorsWe've all been there.
Frequently Asked QuestionsReferences
These documents provide a deeper look into Gio.
Gio Internals.
Splitter WidgetWriting a custom widget.
Immediate Mode GUI Programming gioui.org repositorySource Code
Talks
Gio from bottom-up.
GopherCon 2019Portable, Immediate Mode GUI Programs for Mobile and Desktop.
GopherCon UK 2019Demonstrating a Gio program built from scratch.
Community CallsDiscussions on Gio and project demos.
Packages 
Most commonly used packages:
Stateful part of the widgets.
Material themeDrawing of the widget states.
LayoutLaying out the widget drawing
OperationsLow-level primitives of Gio.
ClippingDrawing shapes.
DrawingColoring the shapes.
Pointer inputResponding to mouse and touch events.
Keyboard inputResponding to keyboard events.
GestureDetecting common gestures.