android/proguard-rules.txt

-keepclassmembers class io.grpc.okhttp.OkHttpChannelBuilder {
  io.grpc.okhttp.OkHttpChannelBuilder forTarget(java.lang.String);
  io.grpc.okhttp.OkHttpChannelBuilder scheduledExecutorService(java.util.concurrent.ScheduledExecutorService);
  io.grpc.okhttp.OkHttpChannelBuilder sslSocketFactory(javax.net.ssl.SSLSocketFactory);
  io.grpc.okhttp.OkHttpChannelBuilder transportExecutor(java.util.concurrent.Executor);
}