Obtain an executor with the blocking.never property.

constexpr basic_executor_type require(
    execution::blocking_t::never_t ) const;

Do not call this function directly. It is intended for use with the require customisation point.

For example:

auto ex1 = my_io_context.get_executor();
auto ex2 = boost::asio::require(ex1,
    boost::asio::execution::blocking.never);