DRAFT RELEASE NOTES — Introduction to Go 1.21

Go 1.21 is not yet released. These are work-in-progress release notes. Go 1.21 is expected to be released in August 2023.

Changes to the language

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Ports

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Tools

Go command

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Runtime

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When printing very deep stacks, the runtime now prints the first 50 (innermost) frames followed by the bottom 50 (outermost) frames, rather than just printing the first 100 frames. This makes it easier to see how deeply recursive stacks started, and is especially valuable for debugging stack overflows.

Compiler

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Linker

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Core library

Minor changes to the library

As always, there are various minor changes and updates to the library, made with the Go 1 promise of compatibility in mind. There are also various performance improvements, not enumerated here.

TODO: complete this section

sync

The new OnceFunc, OnceValue, and OnceValues functions capture a common use of Once to lazily initialize a value on first use.