There have been a number of requests for a test dependencies section in go.mod. These requests actually don't make sense with the way that go.mod works, because it's really just a list of rules to follow for resolving dependencies, not a list of dependencies. The actual list of dependencies is per-package, not per-module, and is determined by the actual import statements in the code itself. The go tool, however, does add some extra information to the go.mod file in the form of an // indirect comment after dependencies that are only depended on by a dependency.

I propose adding an alternate comment flag, test, to indicate that a dependency is only required by tests. Along with this, add an indication of this to the Module struct used for formatting go list -m output.