How to make keystroke for Flutter app? 

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keytool -genkey -v -keystore c:\Users\USER_NAME\upload-keystore.jks -storetype JKS -keyalg RSA -keysize 2048 -validity 10000 -alias upload
Generate an upload key and keystore
If you don't already have an upload key, which is useful when configuring Play App Signing, you can generate one using Android Studio as follows:
In the menu bar, click Build and Generate Signed Bundle/APK.
In the Generate Signed Bundle or APK dialog, select Android App Bundle or APK and click Next.
Below the field for Key store path, click Create new.
On the New Key Store window, provide the following information for your keystore and key, as shown in figure 2.
Figure 2. Create a new upload key and keystore in Android Studio.
Keystore
Key store path: Select the location where your keystore should be created.
Password: Create and confirm a secure password for your keystore.
Key
Alias: Enter an identifying name for your key.
Password: Create and confirm a secure password for your key. This should be different from the password you chose for your keystore.
Validity (years): Set the length of time in years that your key will be valid. Your key should be valid for at least 25 years, so you can sign app updates with the same key through the lifespan of your app.
Certificate: Enter some information about yourself for your certificate. This information is not displayed in your app, but is included in your certificate as part of the APK.
Once you complete the form, click OK.
If you would like to build and sign your app with your upload key, continue to the section about how to Sign your app with your upload key. If you only want to generate the key and keystore, click Cancel.