Network Api Service with Retrofit

ApiService.kt

package com.vk.android.network


import com.vk.android.BuildConfig
import io.reactivex.Observable
import okhttp3.OkHttpClient
import okhttp3.logging.HttpLoggingInterceptor
import retrofit2.Retrofit
import retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory
import retrofit2.converter.gson.GsonConverterFactory
import retrofit2.http.Body
import retrofit2.http.Headers
import retrofit2.http.POST
import java.util.concurrent.TimeUnit


interface ApiService {

    @Headers("Content-Type:application/json;charset=UTF-8")
    @POST("api/register")
    fun signUp(@Body map: HashMap<String, Any?>): Observable<Any>


    companion object Factory {
        private var apiService: ApiService? = null
        private val okHttpClient = OkHttpClient.Builder()
            .connectTimeout(31, TimeUnit.SECONDS)
            .readTimeout(30, TimeUnit.SECONDS)
            .writeTimeout(30, TimeUnit.SECONDS)

        fun create(): ApiService {
            if (apiService == null) {
                if (BuildConfig.DEBUG) {
                    val httpLog = HttpLoggingInterceptor()
                    httpLog.setLevel(HttpLoggingInterceptor.Level.BODY)
                    okHttpClient.addInterceptor(httpLog)
                }
                val retrofit = Retrofit.Builder()
                    .client(okHttpClient.build())
                    .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                    .addConverterFactory(GsonConverterFactory.create())
                    .baseUrl(BuildConfig.BASE_URL)
                    .build()

                apiService = retrofit.create(ApiService::class.java);
            }

            return apiService!!
        }
    }
}