Error connecting to the service protocol: Exception: Attempted to connect to Dart observatory 5 times, and all attempts failed. Giving up. The URL was ws://127.0.0.1:8111/ws如果运行后输出 Log 是这样，同时使用了代理，那问题就是代理设置造成的，需要将 127.0.0.1 排除出代理
修改环境变量
sudo nano /etc/profile添加
export no_proxy="localhost,127.0.0.1"