lsp-test: Catch timeout on no message?

In my program which uses lsp-test, I need to wait for either of the following conditions to be true:

* server sends a textDocument/publishDiagnostics notification
* 1 second elapses

How can I implement this with lsp-test?

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I tried adding an API to lsp-test to make what I want possible. However, my implementation has problems. In short, it seems that conduit-parser is not well-suited for this task because alternatives can't "sleep"; calling `await` blocks all alternatives. Here's the code, including a failing test demonstrating some problems with my API: https://github.com/haskell/lsp/commit/06e222435c1423768c28de485044693a0f3ec68b

Start with the failing test and attempted lsp-test API in commit 06e222435c1423768c28de485044693a0f3ec68b. Investigate how conduit-parser handles alternatives and whether await blocks them; done means lsp-test can wait for a textDocument/publishDiagnostics notification or return after one second.

Written by the indexing model from the issue text.