DRAFT RELEASE NOTES — Introduction to Go 1.16

Go 1.16 is not yet released. These are work-in-progress release notes. Go 1.16 is expected to be released in February 2021.

Changes to the language

TODO

Ports

TODO

Tools

TODO

Go command

retract directives may now be used in a go.mod file to indicate that certain published versions of the module should not be used by other modules. A module author may retract a version after a severe problem is discovered or if the version was published unintentionally.
TODO: write and link to section in golang.org/ref/mod
TODO: write and link to tutorial or blog post

TODO

Runtime

TODO

Compiler

TODO

Linker

This release includes additional improvements to the Go linker, reducing linker resource usage (both time and memory) and improving code robustness/maintainability. These changes form the second half of a two-release project to modernize the Go linker.

The linker changes in 1.16 extend the 1.15 improvements to all supported architecture/OS combinations (the 1.15 performance improvements were primarily focused on ELF-based OSes and amd64 architectures). For a representative set of large Go programs, linking is 20-35% faster than 1.15 and requires 5-15% less memory on average for linux/amd64, with larger improvements for other architectures and OSes.

TODO: update with final numbers later in the release.

Core library

TODO

unicode

The unicode package and associated support throughout the system has been upgraded from Unicode 12.0.0 to Unicode 13.0.0, which adds 5,930 new characters, including four new scripts, and 55 new emoji. Unicode 13.0.0 also designates plane 3 (U+30000-U+3FFFF) as the tertiary ideographic plane.

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.

TODO

In the net/http package, the behavior of StripPrefix has been changed to strip the prefix from the request URL's RawPath field in addition to its Path field. In past releases, only the Path field was trimmed, and so if the request URL contained any escaped characters the URL would be modified to have mismatched Path and RawPath fields. In Go 1.16, StripPrefix trims both fields. If there are escaped characters in the prefix part of the request URL the handler serves a 404 instead of its previous behavior of invoking the underlying handler with a mismatched Path/RawPath pair.