GCP Terraform appengine

I am writing the code for terraform flexible appengine. in my terraform code, it is getting failed with error " appyaml file not found.:

Starting Step #1

Step #1: Pulling image: Google Cloud Platform

Step #1: gcr.io/gcp-runtimes/python/gen-dockerfile@sha256:ac444fc620f70ff80c19cde48d18242dbed63056e434f0039bf939433e7464aa: Pulling from gcp-runtimes/python/gen-dockerfile

Step #1: Digest: sha256:ac444fc620f70ff80c19cde48d18242dbed63056e434f0039bf939433e7464aa

Step #1: Status: Downloaded newer image for Google Cloud Platform

Step #1: Google Cloud Platform

Step #1: Traceback (most recent call last):

Step #1: File “/builder/gen_dockerfile.py”, line 277, in

Step #1: main()

Step #1: File “/builder/gen_dockerfile.py”, line 273, in main

Step #1: generate_dockerfile_command(args.base_image, args.config, args.source_dir)

Step #1: File “/builder/gen_dockerfile.py”, line 220, in generate_dockerfile_command

Step #1: with io.open(config_file, ‘r’, encoding=‘utf8’) as yaml_config_file:

Step #1: FileNotFoundError: [Errno 2] No such file or directory: ‘./hello-world/app.yaml’

Finished Step #1

Please give your suggestion to resolve this issue.