Function streaming

streaming('wss://example.test/live', () => 'unreachable')
    .onOpen(socket => socket.send(subscribe))
    .onMessage(receive)
    .onClose(mourn);
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streaming owns a socket's whole life: the handshake, the flow, the ending. Message policy stays with the caller — frames arrive raw. Settled facts replay for late listeners; the flow does not. close is the one teardown, silent and idempotent: our own hanging up is not an ending worth announcing.