curl: (56) LibreSSL SSL_read: SSL_ERROR_SYSCALL, errno 54

输入flutter run报错

mm@mmdeMacBook-Pro lovebusiness % flutter run
Downloading Dart SDK from Flutter engine ae90085a8437c0ae94d6b5ad2741739ebc742cb4...
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:--  0:03:02 --:--:--     0
curl: (56) LibreSSL SSL_read: SSL_ERROR_SYSCALL, errno 54

Failed to retrieve the Dart SDK from: https://storage.googleapis.com/flutter_infra/flutter/ae90085a8437c0ae94d6b5ad2741739ebc742cb4/dart-sdk-darwin-x64.zip
If you're located in China, please see this page:
  https://flutter.dev/community/china

在项目根目录下的终端依次输入：

　　

export PUB_HOSTED_URL=https://pub.flutter-io.cn
export FLUTTER_STORAGE_BASE_URL=https://storage.flutter-io.cn

然后就可以正常下载了