Unable to run flutter app after i got it read for export to Google Play Store

I flowed the guide on how to publish a flutter app to google play store from flutter docs. I changed every thing for the key.properties file. This is the build.gradle file:

plugins {
    id "com.android.application"
    id "kotlin-android"
    id "dev.flutter.flutter-gradle-plugin"
}

def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
    localPropertiesFile.withReader('UTF-8') { reader ->
        localProperties.load(reader)
    }
}

def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
if (flutterVersionCode == null) {
    flutterVersionCode = '1'
}

def flutterVersionName = localProperties.getProperty('flutter.versionName')
if (flutterVersionName == null) {
    flutterVersionName = '1.0'
}

def keystoreProperties = new Properties()
   def keystorePropertiesFile = rootProject.file('key.properties')
   if (keystorePropertiesFile.exists()) {
       keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
   }


android {
    namespace "com.example.flutter_food_app"
    compileSdkVersion flutter.compileSdkVersion
    ndkVersion flutter.ndkVersion

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = '1.8'
    }

    sourceSets {
        main.java.srcDirs += 'src/main/kotlin'
    }

    defaultConfig {
        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
        applicationId "com.example.flutter_food_app"
        // You can update the following values to match your application needs.
        // For more information, see: https://docs.flutter.dev/deployment/android#reviewing-the-gradle-build-configuration.
        minSdkVersion flutter.minSdkVersion
        targetSdkVersion flutter.targetSdkVersion
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
    }

    signingConfigs {
        release {
           keyAlias keystoreProperties['keyAlias']
           keyPassword keystoreProperties['keyPassword']
           storeFile keystoreProperties['storeFile'] ? file(keystoreProperties['storeFile']) : null
           storePassword keystoreProperties['storePassword']
        }
    }
    buildTypes {
       release {
           signingConfig signingConfigs.release
       }
    }
}

flutter {
    source '../..'
}

dependencies {}

This is the Error code i am getting

Launching lib\main.dart on sdk gphone64 x86 64 in debug mode...

FAILURE: Build failed with an exception.

* Where:
Build file 'stuff to\android\app\build.gradle' line: 28

* What went wrong:
A problem occurred evaluating project ':app'.
> Malformed \uxxxx encoding.

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 9s
Exception: Gradle task assembleDebug failed with exit code 1


Exited (1).

I have tried trouble shooting by commenting out sign config and keystoreProperties it works then but when i uncomment either. I get the same error but different line on one of them. I have tried googling and could not find an answer that would worked.

If your keystore file name is upload-keystore.jks then just use \ before in the key.properties file

Use :

storePassword=<password>
keyPassword=<password>
keyAlias=upload
storeFile=\\upload-keystore.jks

Replace the code in the key.properties file