title: go module dependency another local directory
body: <p>I have the following folders:</p>
  <pre><code>folder1:
     go.sum
     go.mod
     main.go
  
  folder2:
     proto.pb.go
  </code></pre>
  <p>How in folder1 can I add the proto.pb.go as a dependency, so that files in folder1 can access to proto.pb.go?</p>