(Deprecated: Use expiry().) Get the timer's expiry time relative to now.

duration expires_from_now() const;
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(Deprecated: Use expires_after().) Set the timer's expiry time relative to now.

std::size_t expires_from_now(
    const duration & expiry_time);
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std::size_t expires_from_now(
    const duration & expiry_time,
    asio::error_code & ec);
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