我最近下载了flutter SDK，一切顺利，直到克隆了一个试图获取软件包的项目为止。它只是一次又一次失败。 我可以通过浏览器访问该网站，所以这不是代理问题。
有什么想法吗？ 这是错误：
pub get failed (69) -- attempting retry 1 in 1 second...
Running "flutter pub get" in ethio_scholars_flutter_app.Got socket error trying to find package string_scanner at https://pub.dartlang.org.
pub get failed (69) -- attempting retry 2 in 2 seconds...
Got socket error trying to find package string_scanner at https://pub.dartlang.org.
pub get failed (69) -- attempting retry 3 in 4 seconds...
Got socket error trying to find package string_scanner at https://pub.dartlang.org.
pub get failed (69) -- attempting retry 4 in 8 seconds... ```