title: go-grpc Import "google/protobuf/struct.proto" was not found or had errors
body: <p>I'm using following command to generate proto code for golang:</p>
  <pre><code>protoc --go_out=../generated --go_opt=paths=source_relative \
      --go-grpc_out=../generated --go-grpc_opt=paths=source_relative \
      *.proto
  </code></pre>
  <p>I'm using in-built google/protobuf/struct.proto for unstructured data. However, I'm getting an error saying &quot;google.protobuf.Struct&quot; is not defined.</p>