app instantly closees react native code example

Example 1: react native app crashes without error

in react native node-modules go 
 node modules >>  react -native-admob>> android >>Build.gradle 
instead of follwing line
'com.google.android.gms:play-services-ads:+'

write this line 
'com.google.android.gms:play-services-ads:16.0.0'

Example 2: expo create react native app

npm install --global expo-cli

expo init my-project