Server should send RST_STREAM when deadline is exceeded

[ejona86]

The server code relies on the application to return when the deadline is exceeded. But when it does return, it doesn't cancel the RPC; it sends a graceful close:
https://github.com/grpc/grpc-go/blob/v1.21.1/server.go#L1010

If the deadline is exceeded when the handler returns, the RPC should be cancelled and RST_STREAM should be sent (if one hasn't already been received from the client).

[ejona86]

Note that this may have interactions with ServerInHandle, if ServerInHandle changes the deadline. It is only appropriate to use RST_STREAM when the client specified its deadline, since in that case the client will ignore what the server sends anyway. If the ServerInHandler reduced the deadline, then a normal close is appropriate.

[infovivek2020]

@purnesh42H Please assign to me