GoPathError = "cannot set GOROOT as GOPATH"
		}
		return ""
	}
	GoPathError = fmt.Sprintf("%s is not set", env)
	return ""
}

// WithBuildXWriter returns a Context in which BuildX output is written
// to given io.Writer.
func WithBuildXWriter(ctx context.Context, xLog io.Writer) context.Context {
	return context.WithValue(ctx, buildXContextKey{}, xLog)
}

type buildXContextKey struct{}

	cfg.GOMODCACHE = filepath.Join(dir, "modcache")
	cfg.ModCacheRW = true

	m.Run()
	return nil
}

func testContext(t testing.TB) context.Context {
	w := newTestWriter(t)
	return cfg.WithBuildXWriter(context.Background(), w)
}

// A testWriter is an io.Writer that writes to a test's log.
//
// The writer batches written data until the last byte of a write is a newline