Flutter upgrade 升级慢卡死的问题
1.删除flutter SDK 中的bin/cache 然后再 flutter upgrade
2.找到flutter SDK 文件夹 git pull -> git reset —hard 版本号
版本号参考：https://github.com/flutter/flutter/releases?after=1.20.0-7.1.pre -> flutter doctor
1.删除flutter SDK 中的bin/cache 然后再 flutter upgrade
2.找到flutter SDK 文件夹 git pull -> git reset —hard 版本号
版本号参考：https://github.com/flutter/flutter/releases?after=1.20.0-7.1.pre -> flutter doctor
