cmd/go/internal/modload: cache the Go language version for each module globally

Previously, this cache was a member of the (ephemeral) modload.loader
struct. However, the Go language version for a given module version
does not vary based on the build list, the set of loaded packages, the
build tags in use, the meaning of the "all" pattern, or anything else
that can be configured for an instance of the package loader. The map
containing that information is therefore not appropriate as a field of
the (configurable, package-list-dependent) loader struct.

The Go language version mapping could, in theory, be read from the
go.mod file in the module cache (or replacement directory) every time
it is needed: this map is just a cache, and as such it belongs
alongside the other caches and indexes in the modload package, which
are currently found in modfile.go.

We may want to do the same sort of global caching for the mapping from
each module.Version to its list of direct requirements (which are
similarly idempotent), but for now that is left for a future change.

For #36460
For #36876

Change-Id: I90ac176ffea97f30c47d6540c3dfb874dc9cfa4f
Reviewed-by: Jay Conrod <>
Reviewed-by: Michael Matloob <>
4 files changed
tree: efd5c630066050839754cc543998487c06cca11a
  1. .gitattributes
  2. .github/
  3. .gitignore
  11. api/
  12. doc/
  13. favicon.ico
  14. lib/
  15. misc/
  16. robots.txt
  17. src/
  18. test/

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

Gopher image Gopher image by Renee French, licensed under Creative Commons 3.0 Attributions license.

Our canonical Git repository is located at There is a mirror of the repository at

Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.

Download and Install

Binary Distributions

Official binary distributions are available at

After downloading a binary release, visit or load doc/install.html in your web browser for installation instructions.

Install From Source

If a binary distribution is not available for your combination of operating system and architecture, visit or load doc/install-source.html in your web browser for source installation instructions.


Go is the work of thousands of contributors. We appreciate your help!

To contribute, please read the contribution guidelines:

Note that the Go project uses the issue tracker for bug reports and proposals only. See for a list of places to ask questions about the Go language.