--- title: "Composite keys" url: https://daily.dev/posts/composite-keys-xh0zxyhc6 source_url: https://boldlygo.tech/archive/2023-09-22-composite-keys type: article source: "Boldly Go" published: 2026-05-31T07:49:35.916Z updated: 2026-05-31T09:15:34.693Z tags: ["golang", "data-structures"] reading_time: 2 upvotes: 0 comments: 0 language: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Composite keys **[Boldly Go](https://daily.dev/sources/boldlygo)** · 2 min read · 0 upvotes · 0 comments ## Summary Go composite literals support keys in more contexts than most developers realize. While map keys and struct field names are well-known, array and slice literals also support integer keys that specify element indices. This allows sparse population of slices/arrays or out-of-order element specification, as demonstrated with a concrete code example showing how unspecified indices default to zero values. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: --- Tags: [#golang](https://daily.dev/tags/golang), [#data-structures](https://daily.dev/tags/data-structures) [View this post on daily.dev](https://daily.dev/posts/composite-keys-xh0zxyhc6)