Your flutter checkout has local changes that would be erased by upgrading. If you want to keep these changes, it is recommended that you stash them via "git stash" or else
commit the changes to a local branch. If it is okay to remove local changes, then re-run this command with --force.

在使用第三方库的时候，说是flutter sdk版本不够，于是我输入 flutter upgrade指令，以上就是报错信息
解决方法：加上--force，强制升级

flutter upgrade --force