feat: router groups

[joseph-beck]

Adds router groups to amp!

Create a router group with

func main() {
	g := amp.Group("/group")
	g.Get("/hello", func(ctx *amp.Ctx) error {
		return ctx.Render(200, "hello world!")
	})

	a := amp.New()

	a.Group(g)

	log.Fatalln(a.ListenAndServe())
}

[Copilot]

Pull request overview

This PR adds router groups functionality to the amp web framework, allowing developers to organize routes under common prefixes with shared middleware. This is a common pattern in web frameworks that improves code organization and reduces duplication.

Key changes:

• Introduces a new group type and Group() function for creating route groups with prefixes and middleware
• Adds Mux.Group() method to register groups with the router
• Includes comprehensive unit tests for all group methods

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
pkg/amp/group.go	Defines the core group types and methods for creating and managing route groups with HTTP method handlers
pkg/amp/group_test.go	Comprehensive unit tests for all group struct methods and functionality
pkg/amp/mux.go	Adds Mux.Group() method to register groups and additional logging for server startup
go.mod	Updates Go version to 1.25
.github/workflows/go.yml	Updates CI workflow to use Go 1.25 and reformats YAML structure
examples/group/main.go	Demonstrates usage of the new router groups feature
examples/group/README.md	Brief documentation for the group example

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