Header field token is not allowed by access-control-allow-headers in preflight response problem resolution

This afternoon, I was going to use Aioxs to send a token to the backend server in the header, as shown in:

As a result, the console reported the following error:

Then, I keep on Baidu, constantly change the background Express header set, has no effect;

Finally, I found that I just set the original header to add a ' token ' on it;

Specific ideas I was referring to this link: https://segmentfault.com/q/1010000015572348?sort=created

Header field token is not allowed by access-control-allow-headers in preflight response problem resolution