feat(blog): add "What's New in Go 1.27" post

[iwanhae]

Summary

• Adds a new English blog post covering the Go 1.27 release, from the language changes through the toolchain
• Every code example and output block was executed against go1.27rc3 (darwin/arm64) instead of being transcribed from the release notes
• Adds the release overview graphic as overview.webp

Why

Go 1.27 is the first release in a while that changes the language itself — generic methods close the last major gap left by the 1.18 generics work, and struct literal field selectors resolve an issue that had been open since 2015. Alongside that, encoding/json was rebuilt on a new v2 implementation, uuid landed in the standard library, and the goroutine leak profile went GA.

Release notes tell you what changed but not what it feels like to use, where the sharp edges are, or which items are actually worth acting on first. This post fills that gap for readers deciding whether and how to upgrade.

Running everything against the release candidate also surfaced a correction worth having in writing: several summaries circulating online claim that encoding/json v1 became stricter in 1.27 and now rejects duplicate keys and invalid UTF-8. It does not. v1 behavior is fully preserved — Unmarshal always applies DefaultOptionsV1() — and the stricter defaults belong to the new v2 package. The post documents the verified behavior.

Changes

• Add root/blog/whats-new-in-go1.27.md
• Add public/assets/images/whats-new-in-go1.27/overview.webp
• Language section: generic methods (including the verified compiler error showing they cannot implement interface methods), struct literal field selectors with all four accept/reject cases compiled individually, generalized function type inference
• Runtime section: size-specialized allocation with measured benchmarks (5.36ns vs 8.72ns) and binary size delta (~50KB), goroutine leak profile, traceback goroutine labels, asynctimerchan removal and the new removed-GODEBUG policy
• Standard library section: the three-package encoding/json structure and incremental migration path, uuid, crypto/mldsa with real key and signature sizes, experimental simd, hash/maphash.Hasher, httptest.NewTestServer + synctest.Sleep, plus the smaller net/http, strings, math/big, and net/url additions
• Toolchain section: go fix modernizers with an actual -diff, stdversion in go test, -json OutputType, go doc improvements, go mod tidy require-block merging
• Compiler, linker, and port changes, followed by an upgrade checklist

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