今天升级Flutter的时候发生了报错，具体错误信息如下：
ProcessException: Process exited abnormally:
fatal: unable to access 'https://github.com/flutter/flutter.git/': LibreSSL SSL_connect: SSL_ERROR_SYSCALL in connection to github.com:443
Command: git fetch --tags
根据调查应该是使用了代理的问题导致的，解决方案：
- 先使用
git config --global --add remote.origin.proxy命令关闭代理； - 再执行
flutter upgrade命令执行升级。
示例如下：
git config --global --add remote.origin.proxy ""
flutter upgrade
执行以上命令后，问题就能顺利解决了，您将看到以下信息：
Upgrading Flutter to 2.0.6 from 2.0.1 in /Users/tyyod/Library/flutter...
Downloading Dart SDK from Flutter engine 05e680e202af9a92461070cb2d9982acad46c83c...
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
0 194M 0 510k 0 0 321k 0 0:10:20 0:00:01 0:10:19 321k
0 194M 0 1787k 0 0 691k 0 0:04:48 0:00:02 0:04:46 690k
1 194M 1 3519k 0 0 981k 0 0:03:23 0:00:03 0:03:20 981k
2 194M 2 5607k 0 0 1222k 0 0:02:43 0:00:04 0:02:39 1221k
4 194M 4 8163k 0 0 1460k 0 0:02:16 0:00:05 0:02:11 1660k
5 194M 5 10.4M 0 0 1628k 0 0:02:02 0:00:06 0:01:56 2043k
6 194M 6 13.3M 0 0 1800k 0 0:01:50 0:00:07 0:01:43 2375k
8 194M 8 16.6M 0 0 1979k 0 0:01:40 0:00:08 0:01:32 2694k
10 194M 10 19.7M 0 0 2109k 0 0:01:34 0:00:09 0:01:25 2924k
11 194M 11 22.9M 0 0 2216k 0 0:01:29 0:00:10 0:01:19 3062k
13 194M 13 27.1M 0 0 2401k 0 0:01:22 0:00:11 0:01:11 3419k
16 194M 16 31.8M 0 0 2595k 0 0:01:16 0:00:12 0:01:04 3800k
19 194M 19 37.5M 0 0 2832k 0 0:01:10 0:00:13 0:00:57 4297k
22 194M 22 43.8M 0 0 3079k 0 0:01:04 0:00:14 0:00:50 4939k
25 194M 25 50.1M 0 0 3294k 0 0:01:00 0:00:15 0:00:45 5576k
29 194M 29 57.7M 0 0 3564k 0 0:00:55 0:00:16 0:00:39 6259k
33 194M 33 65.0M 0 0 3786k 0 0:00:52 0:00:17 0:00:35 6784k
37 194M 37 73.4M 0 0 4049k 0 0:00:49 0:00:18 0:00:31 7358k
41 194M 41 80.9M 0 0 4233k 0 0:00:47 0:00:19 0:00:28 7600k
44 194M 44 86.9M 0 0 4322k 0 0:00:46 0:00:20 0:00:26 7519k
48 194M 48 93.5M 0 0 4439k 0 0:00:44 0:00:21 0:00:23 7340k
52 194M 52 101M 0 0 4594k 0 0:00:43 0:00:22 0:00:21 7436k
55 194M 55 108M 0 0 4692k 0 0:00:42 0:00:23 0:00:19 7084k
59 194M 59 115M 0 0 4795k 0 0:00:41 0:00:24 0:00:17 6994k
61 194M 61 119M 0 0 4790k 0 0:00:41 0:00:25 0:00:16 6722k
63 194M 63 123M 0 0 4744k 0 0:00:41 0:00:26 0:00:15 6064k
66 194M 66 129M 0 0 4825k 0 0:00:41 0:00:27 0:00:14 5868k
70 194M 70 136M 0 0 4893k 0 0:00:40 0:00:28 0:00:12 5838k
73 194M 73 143M 0 0 4974k 0 0:00:40 0:00:29 0:00:11 5852k
77 194M 77 151M 0 0 5063k 0 0:00:39 0:00:30 0:00:09 6460k
81 194M 81 158M 0 0 5140k 0 0:00:38 0:00:31 0:00:07 7240k
85 194M 85 166M 0 0 5232k 0 0:00:38 0:00:32 0:00:06 7476k
89 194M 89 174M 0 0 5312k 0 0:00:37 0:00:33 0:00:04 7711k
93 194M 93 181M 0 0 5388k 0 0:00:36 0:00:34 0:00:02 7839k
97 194M 97 190M 0 0 5467k 0 0:00:36 0:00:35 0:00:01 7943k
100 194M 100 194M 0 0 5515k 0 0:00:36 0:00:36 --:--:-- 8135k
Building flutter tool...
Upgrading engine...
Flutter assets will be downloaded from https://storage.flutter-io.cn. Make sure you trust this source!
Downloading android-arm-profile/darwin-x64 tools... 1,337ms
Downloading android-arm-release/darwin-x64 tools... 1,275ms
Downloading android-arm64-profile/darwin-x64 tools... 1,729ms
Downloading android-arm64-release/darwin-x64 tools... 941ms
Downloading android-x64-profile/darwin-x64 tools... 763ms
Downloading android-x64-release/darwin-x64 tools... 1,611ms
Downloading android-x86 tools... 4.8s
Downloading android-x64 tools... 4.9s
Downloading android-arm tools... 2,490ms
Downloading android-arm-profile tools... 1,158ms
Downloading android-arm-release tools... 865ms
Downloading android-arm64 tools... 1,884ms
Downloading android-arm64-profile tools... 1,117ms
Downloading android-arm64-release tools... 994ms
Downloading android-x64-profile tools... 1,184ms
Downloading android-x64-release tools... 1,626ms
Downloading android-x86-jit-release tools... 6.0s
Downloading ios tools... 11.6s
Downloading ios-profile tools... 7.6s
Downloading ios-release tools... 32.9s
Downloading Web SDK... 6.2s
Flutter 2.0.6 • channel stable • https://github.com/flutter/flutter.git
Framework • revision 1d9032c7e1 (7 days ago) • 2021-04-29 17:37:58 -0700
Engine • revision 05e680e202
Tools • Dart 2.12.3
Running flutter doctor...
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 2.0.6, on Mac OS X 10.15.7 19H524 darwin-x64, locale zh-Hans-CN)
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
[✓] Xcode - develop for iOS and macOS
[✓] Chrome - develop for the web
[✓] Android Studio (version 4.1)
[✓] IntelliJ IDEA Ultimate Edition (version 2020.3.3)
[✓] VS Code (version 1.54.3)
[✓] Connected device (2 available)
• No issues found!
