I’m trying to configure Firebase with my Flutter project. However, I’m facing an error when I open the project’s build.gradle file; it doesn’t show me the buildscript function to add the dependencies. I have watched a lot of YouTube videos, but I haven’t been able to find a solution, so I’m writing my problem here.

Here is the code of project’s build.gradle file:

allprojects {
    repositories {
        google()
        mavenCentral()
    }
}

rootProject.buildDir = '../build'
subprojects {
    project.buildDir = "${rootProject.buildDir}/${project.name}"
}

subprojects {
    project.evaluationDependsOn(':app')
}

tasks.register("clean", Delete) {
    delete rootProject.buildDir
}

That’s the error:
Plugin [id: 'com.google.gms.google-services'] was not found in any of the following source

I have tried many times to add dependencies in build.gradle, but it starts with allprojects and there is no buildscript function present. I tried to manually add the buildscript function at the Android-level build.gradle, but it shows errors. What should I do?