cmd/go: refactor modload.Import for better -mod=readonly errors

When -mod=readonly is set, Import will now allow imports from
replacements without explicit requirements. With -mod=mod, this would
add a new requirement but does not trigger a module lookup, so it's

Before reporting an error for an unknown import with -mod=readonly,
check whether the import is valid. If there's a typo in the import,
that's more relevant.

For #40728

Change-Id: I05e138ff76ba3d0eb2e3010c15589fa363deb8d3
Run-TryBot: Jay Conrod <>
TryBot-Result: Gobot Gobot <>
Reviewed-by: Michael Matloob <>
Reviewed-by: Bryan C. Mills <>
2 files changed
tree: 68f54fea4b32ad75f5f8196b95d14ab6dcdf47a2
  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.