title: go test fails with "can't load package build constraints exclude all Go files"
body: <p>When I run this command</p>
  
  <pre><code>go test -tags integration $(go list ./... | grep -v /vendor/)
  </code></pre>
  
  <p>go fails with this for some packages that has all tests marked with <code>// +build !integration</code></p>
  
  <pre><code>can't load package: build constraints exclude all Go files
  </code></pre>
  
  <p>Is there a way I can make <code>go test</code> ignore those packages in this case, instead of failing?  Thanks</p>