proposal: container/...: generic collection types

Updates: including insertion-ordered maps, and specifying JSON marshaling behavior. 13 Oct 2026. -jba Updated with the latest changes. 7 Oct 2026. -jba ---- **Background:** The Go Collections working group was formed in late 2025 with the purpose of bringing common collection data structures to the standard library, guided by the familiar Go principles of pragmatism and simplicity. Alphabetically by last name, the group consists of Jonathan Amsterdam (@jba), Alan Donovan (@adonovan), Robert Griesemer (@griesemer), Daniel Martí (@mvdan), Roger Peppe (@rogpeppe), Keith Randall (@khr), and Ian Lance Taylor (@ianlancetaylor). We’ve now reached a point where we’re ready to share our results with the community. This issue is an umbrella for discussing several related proposals for new collections APIs for Go 1.28. It presents a high level overview of the themes, and links to the various concrete proposals and associated implementation CLs. Go currently provides few collection types in its library, and from the outset we have emphasized the flexibility of the language’s built-in slice and map types. Of those provided, the most important is the heap, used for priority queues. Even sets are absent; they are conventionally expressed in terms of map\[T\]bool or map\[T\]struct{}. Ordered maps and sets based on binary trees are entirely absent. Since the addition of generics in Go 1.18 and iterators in Go 1.23, it has become possible for library-defined types to achieve comparable er

Posted by adonovan on Jul 28, 2026, 4:12 AM

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