#### basic_yield_context::operator[]

Return a yield context that sets the specified error_code.

    basic_yield_context operator[](
        asio::error_code & ec) const;

By default, when a yield context is used with an asynchronous operation, a non-success error_code is converted to system_error and thrown. This operator may be used to specify an error_code object that should instead be set with the asynchronous operation's result. For example:

    template <typename Executor>
    void my_coroutine(basic_yield_context<Executor> yield)
    {
      ...
      std::size_t n = my_socket.async_read_some(buffer, yield[ec]);
      if (ec)
      {
        // An error occurred.
      }
      ...
    }