But the linked close works on Streams not PendingConnections. To get a PendingConnection's Stream you must use pendingStream which is only exported by Network.WebSockets.Connection which has a scary warning at the top that you shouldn't use be importing it unless you know what you're doing.
The docs state
https://github.com/jaspervdj/websockets/blob/ff17c79840997dfa50e0854edcd239e3294dc950/src/Network/WebSockets/Server.hs#L203
But the linked
closeworks onStreams notPendingConnections. To get aPendingConnection'sStreamyou must usependingStreamwhich is only exported byNetwork.WebSockets.Connectionwhich has a scary warning at the top that you shouldn't use be importing it unless you know what you're doing.