export

FLUTTER_STORAGE_BASE_URL

=https://storage.flutter-io.cn

git clone

b dev https://github.com/flutter/flutter.git

export

PATH

$PWD

/flutter/bin:

$PATH

cd ./flutter

flutter doctor

After these steps, you should be able to continue
setting up Flutter normally.
From here on, packages fetched by flutter pub get are
downloaded from flutter-io.cn in any shell where PUB_HOSTED_URL
and FLUTTER_STORAGE_BASE_URL are set.