Protobuf import failure : <p>Does anyone know where I can find an example of a gRPC protobuf file that imports from a different file and uses a protobuf message in a return? I can't find any at all.</p>

<p>I have a file...</p>

<pre><code>syntax = "proto3";
package a1;
import "a.proto";
service mainservice {
  rpc DoSomething(...) returns (a.SomeResponse) {}


}
</code></pre>

<p>a.proto is also in the same directory and also compiles by itself. The error messages I'm getting are:
  <code>"a.SomeResponse" is not defined.</code>
  <code>mainfile.proto: warning: Import a.proto but not used.</code></p>
