Set the timer's expiry time relative to now.

std::size_t expires_from_now(
    const duration_type & expiry_time,
    boost::system::error_code & ec);

This function sets the expiry time. Any pending asynchronous wait operations will be cancelled. The handler for each cancelled operation will be invoked with the boost::asio::error::operation_aborted error code.

Parameters

Return Value

The number of asynchronous operations that were cancelled.