Log.txt

System.out: DEBUG: ApiService: 98713473 // on App start
System.out: DEBUG: ApiService: 98713473 // Rotate
System.out: DEBUG: ApiService: 98713473 // Rotate

MainActivity.kt

class MainActivity : AppCompatActivity() {


    lateinit var viewModel: MainViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        viewModel = ViewModelProvider(this).get(MainViewModel::class.java)

        viewModel.user.observe(this, Observer { user ->
            println("DEBUG: ${user}")
        })

        viewModel.setUserId("1")
    }

    override fun onDestroy() {
        super.onDestroy()
        viewModel.cancelJobs()
        viewModel.setUserId("2")
    }
}

Repository.kt

object Repository {

    var job: CompletableJob? = null

    fun getUser(userId: String): LiveData<User>{
        job = Job()
        return object: LiveData<User>(){
            override fun onActive() {
                super.onActive()
                job?.let{ theJob ->
                    CoroutineScope(IO + theJob).launch {
                        val apiService = MyRetrofitBuilder.apiService
                        println("DEBUG: ApiService: ${apiService.hashCode()}")
                        val user = apiService.getUser(userId)
                        withContext(Main){
                            value = user
                            theJob.complete()
                        }
                    }
                }
            }
        }
    }

    fun cancelJobs(){
        job?.cancel()
    }
}