how to access @EnvironmentObject in view's init()

Question

struct ContentView: View {
//    @ObservedObject var user = User()
    @EnvironmentObject var user: User
    
    init(){
        user.username = "yy"
    }

I want change EvironmentObject value in init() cuz I want data preprocessing

but this code has error

Thread 1: Fatal error: No ObservableObject of type User found. A View.environmentObject(_:) for User may be missing as an ancestor of this view.

how can I access EnvironmentObject in View's initialize?