code: func retryGoogleRPC(ctx context.Context, rpcName string, rpc func() error) error {
  	return retry.Retry(ctx, transient.Only(retry.Default), func() error {
  		err := rpc()
  		if gerr, ok := err.(*googleapi.Error); ok && gerr.Code >= 500 {
  			err = transient.Tag.Apply(err)
  		}
  		return err
  	}, retry.LogCallback(ctx, rpcName))
  }
docs: // retryGoogleRPC retries an RPC on transient errors, such as HTTP 500.