[golang] MaxMsgSize error not propagated back through to client

[se...@pachyderm.io]

I'm seeing an error because my client is trying to write a message that is bigger than the `MaxMsgSize` specified when running a GRPC server.

I want to return the descriptive message that I see on the server side when reading off the stream:

```

rpc error: code = 13 desc = grpc: received message length 25165898 exceeding the max size 25165824

```

However, on the client side, using the grpc client's `Send()` method ... I only see an `io.EOF` error.

I've tried having my server API call (part of the GRPC gateway api) return a different error ... but it seems that grpc ignores this and only provides the `io.EOF` error to the client. 

TBH I'm not super familiar w how GRPC implements streams so I could be missing some other detail here. It seems like its possible that the server closes the connection before sending a response and thats why the client see's an EOF. I guess I'm saying its unclear if/why the server is sending an EOF error, and if it is sending any error, I would've expected it to be the error code 13 as above.

For now, I need to have my client report something descriptive when this happens, so the only recourse I have is checking for an EOF error on the client. That ... is not good ... since it seems likely that case could happen for a number of reasons (including a network issue).

[mmu...@google.com]

Hey,

Ideally, the server does write back a status to client when such an error occurs. However, you're write in pointing out that if the stream was closed( due to some other reason), it won't send back the error response. Can you send some more of your log that you see on the server and client side? Also, some snippet of the application code might also help with debugging. 

Best,

Mak