data transfer https://stackoverflow.com/questions/45938931/default-and-specific-request-timeout https://stackoverflow.com/questions/57404925/how-to-increase-http-request-timeout-more-than-2-minutes-in-angular-7 https://stackoverflow.com/questions/48013154/perform-http-get-method-in-angular-with-no-retries-and-wait-until-server-sends-t 人生旅途，边走边看...