这个问题知道怎么回事么。
from origin 'http://localhost:3000' has been blocked by CORS policy: The 'Access-Control-Allow-Origin' header contains multiple values 'http://localhost:3000, *', but only one is allowed. Have the server send the header with a valid value, or, if an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.