Limited compatibility with go < 1.15.10

[kernfeld-cockroach]

When one uses go < 1.15.10 to run go mod tidy, go mod vendor, and possible other go mod * commands in errors or any project that transitively depends on errors, one encounters a failure of the form:

> go mod tidy
github.com/cockroachdb/errors/errbase imports
	io/fs: package io/fs is not in GOROOT (/Users/paulkernfeld/.gvm/gos/go1.14/src/io/fs)

The following snippet from the Go Modules Reference might explain this behavior:

go mod tidy acts as if all build tags are enabled, so it will consider platform-specific source files and files that require custom build tags, even if those source files wouldn’t normally be built.

[kernfeld-cockroach]

A correction: go mod tidy actually does work in go ≥ 1.15.10.

@knz hypothesizes that this is related to golang/go#46143

[knz]

Given that CI is happy with go 1.13 to 1.16, I'm going to close this issue.

[kernfeld-cockroach]

Given that CI is happy with go 1.13 to 1.16, I'm going to close this issue.

Are you saying that it's not important that users of this library be able to successfully run go mod tidy or go mod vendor? I find that counterintuitive because we often use those commands at Cockroach.

[knz]

CI runs successfully with go 1.15.13. I am not too concerned with compatibility with 1.15.9 and prior if 1.15.13 works.