Flutter run error in location package "lambda expressions are not supported in -source 7" How do i enable -source 8

I was importing location package, but due to it not being null-safe i had to change to the latest 4.2.0. All dependencies are null-safe, but the location package creates problem in running on android(both emulator and actual device). As showed in the error message below, "-source 7" does not support lambda expression, but i don't know how to tun it in -source 8. I currently use Visual Studio.

The error message is about lambda expressions in the location package

/home/user/snap/flutter/common/flutter/.pub-cache/hosted/pub.dartlang.org/location-4.2.0/android/src/main/java/com/lyokone/location/FlutterLocation.java:280: error: lambda expressions are not supported in -source 7
            mMessageListener = (message, timestamp) -> {                
                                                    ^                   
  (use -source 8 or higher to enable lambda expressions)                
1 error                                                                 
                                                                        
FAILURE: Build failed with an exception.                                
                                                                        
* What went wrong:                                                      
Execution failed for task ':location:compileDebugJavaWithJavac'.        
> Compilation failed; see the compiler error output for details.        
                                                                        
* 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.

pubspec.yaml file:

dependencies:
  flutter:
    sdk: flutter
provider: ^5.0.0
location: ^4.2.0

part of android/app/build.gradle:

android {
    compileSdkVersion 30

    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.final7"
        minSdkVersion 21
        targetSdkVersion 30
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
    }

    buildTypes {
        release {
            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            signingConfig signingConfigs.debug
        }
    }
}

flutter {
    source '../..'
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
}

part of android/build.gradle:

buildscript {
    ext.kotlin_version = '1.3.50'
    repositories {
        google()
        jcenter()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:4.1.0'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

rootProject.buildDir = '../build'
subprojects {
    project.buildDir = "${rootProject.buildDir}/${project.name}"
    project.evaluationDependsOn(':app')
}

task clean(type: Delete) {
    delete rootProject.buildDir
}