pub get failed (server unavailable) -- attempting retry 2 in 2 seconds...
Could not resolve URL "https://pub.flutter-io.cn".
pub get failed (server unavailable) -- attempting retry 3 in 4 seconds...
Could not resolve URL "https://pub.flutter-io.cn".
pub get failed (server unavailable) -- attempting retry 4 in 8 seconds...
Could not resolve URL "https://pub.flutter-io.cn".
pub get failed (server unavailable) -- attempting retry 5 in 16 seconds...
Could not resolve URL "https://pub.flutter-io.cn".
pub get failed (server unavailable) -- attempting retry 6 in 32 seconds...
Could not resolve URL "https://pub.flutter-io.cn".
pub get failed (server unavailable) -- attempting retry 7 in 64 seconds...
去flutter
目录找到隐藏文件夹 .pub-cache
把缓存删了就可以了