hphp/hack/manual/apis/Functions/HH.Asio/cancel.md
:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::
Cancel Awaitable, if it's still pending
namespace HH\Asio;
function cancel<T>(
Awaitable<T, mixed> $awaitable,
\Exception $exception,
): bool;
If Awaitable has not been completed yet, fails Awaitable with $exception and returns true. Otherwise, returns false.
Throws InvalidArgumentException, if Awaitable does not support cancellation.
Awaitable<T,mixed> $awaitable\Exception $exceptionbool