Update release config for android.

Author: Iiro Krankka

android/app/build.gradle

@@ -14,6 +14,10 @@ if (flutterRoot == null) {
 apply plugin: 'com.android.application'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
+def keystorePropertiesFile = rootProject.file("key.properties")
+def keystoreProperties = new Properties()
+keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
+
 android {
     compileSdkVersion 27
 
@@ -30,11 +34,17 @@ android {
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
     }
 
+    signingConfigs {
+        release {
+            keyAlias keystoreProperties['keyAlias']
+            keyPassword keystoreProperties['keyPassword']
+            storeFile file(keystoreProperties['storeFile'])
+            storePassword keystoreProperties['storePassword']
+        }
+    }
     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
+            signingConfig signingConfigs.release
         }
     }
 }