Update coroutines version to 1.3.9

Author: LukasLechnerDev

app/build.gradle

@@ -42,12 +42,13 @@ android {
 dependencies {
 
     def lifecycle_version = "2.2.0"
+    def coroutines_version = "1.3.9"
 
     implementation fileTree(dir: 'libs', include: ['*.jar'])
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
 
-    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.7"
-    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.7"
+    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:$coroutines_version"
+    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:$coroutines_version"
 
     implementation 'androidx.appcompat:appcompat:1.1.0'
     implementation 'com.google.android.material:material:1.1.0'
@@ -86,7 +87,7 @@ dependencies {
 
     testImplementation 'junit:junit:4.12'
     testImplementation 'androidx.arch.core:core-testing:2.1.0'
-    testImplementation 'org.jetbrains.kotlinx:kotlinx-coroutines-test:1.3.4'
+    testImplementation "org.jetbrains.kotlinx:kotlinx-coroutines-test:$coroutines_version"
     testImplementation 'com.squareup.retrofit2:retrofit-mock:2.7.1'
 
     androidTestImplementation 'androidx.test.ext:junit:1.1.1'