Flutter 项目打包成 Xcode 后，会报 Module ‘flutter_blue’ not found
解决办法是：双击 Runner.xcworkspace 来打开 Xcode 而不是双击 Runner.xcodeproj
那么接下来就会问，.xcodeproj 和 .xcworkspace 有什么区别？
A workspace is a collection of projects. It’s useful to organize your projects when there’s correlation between them (e.g.: Project A includes a library, that is provided as a project itself as project B. When you build the workspace project B is compiled and linked in project A). It’s common to use a workspace in the popular CocoaPods. When you install your pods, they are placed inside a workspace, that holds your project and the pod libraries.