android - Why FirebaseApp initialization is very slow,How to reduce app start time -

i making 1 android app,earlier have used gcm push notification,right trying firebase cloud messaging sending push notifications.i have implemented firebase cloud messaging functionality in app working fine problem is taking time when app launches first time,please me

build.gradle  apply plugin: 'com.android.application'  android {     compilesdkversion 23     buildtoolsversion "23.0.2"      defaultconfig {         applicationid "com.next.fcm"         minsdkversion 15         targetsdkversion 23         versioncode 1         versionname "1.0"         multidexenabled true     }     buildtypes {         release {             minifyenabled false             proguardfiles getdefaultproguardfile('proguard-android.txt'), 'proguard-rules.pro'         }     }     dexoptions {         javamaxheapsize "4g"     }  }  dependencies {     compile filetree(dir: 'libs', include: ['*.jar'])     compile 'com.android.support:appcompat-v7:23.4.0'     compile 'com.android.support:design:23.4.0'      compile 'com.google.firebase:firebase-messaging:9.0.0'  } apply plugin: 'com.google.gms.google-services' 

do not compile whole fcm lib compile below line.

compile "com.google.firebase:firebase-messaging:9.0.0"