Obtain an executor with the relationship.fork property.

basic_system_executor< Blocking, execution::relationship_t::fork_t, Allocator > require(
    execution::relationship_t::fork_t ) const;

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

For example:

boost::asio::system_executor ex1;
auto ex2 = boost::asio::require(ex1,
    boost::asio::execution::relationship.fork);