Migrate extension list fetch to coroutine

app/src/main/java/eu/kanade/tachiyomi/network/OkHttpExtensions.kt

@@ -1,13 +1,14 @@
 package eu.kanade.tachiyomi.network
 
-import okhttp3.Call
-import okhttp3.OkHttpClient
-import okhttp3.Request
-import okhttp3.Response
+import kotlinx.coroutines.suspendCancellableCoroutine
+import okhttp3.*
 import rx.Observable
 import rx.Producer
 import rx.Subscription
+import java.io.IOException
 import java.util.concurrent.atomic.AtomicBoolean
+import kotlin.coroutines.resume
+import kotlin.coroutines.resumeWithException
 
 fun Call.asObservable(): Observable<Response> {
     return Observable.unsafeCreate { subscriber ->
@@ -46,6 +47,31 @@ fun Call.asObservable(): Observable<Response> {
     }
 }
 
+// Based on https://github.com/gildor/kotlin-coroutines-okhttp
+suspend fun Call.await(): Response {
+    return suspendCancellableCoroutine { continuation ->
+        enqueue(object : Callback {
+            override fun onResponse(call: Call, response: Response) {
+                continuation.resume(response)
+            }
+
+            override fun onFailure(call: Call, e: IOException) {
+                // Don't bother with resuming the continuation if it is already cancelled.
+                if (continuation.isCancelled) return
+                continuation.resumeWithException(e)
+            }
+        })
+
+        continuation.invokeOnCancellation {
+            try {
+                cancel()
+            } catch (ex: Throwable) {
+                // Ignore cancel exception
+            }
+        }
+    }
+}
+
 fun Call.asObservableSuccess(): Observable<Response> {
     return asObservable().doOnNext { response ->
         if (!response.isSuccessful) {