Ubuntu – Why is my GitHub Actions workflow not producing any artifacts?

My project in GitHub Actions is going fine, but there is no output (artifact). The essence of all manipulations is as follows – I use the Docker file as a container, I deploy the debian distribution with the iproute2 utility in github actions. The /bin/ss -tulpn command is executed in the container, which receives a list of open ports – the result is written to a file. The file is uploaded to a directory mounted to the container and used as an assembly artifact (packed in tar or deb). Output: workflow file, Dockerfile, successfully completed actions process, artifact, in one of the formats.

build.yml

name: Build and Package

on: [push]

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
    - name: Checkout code
      uses: actions/checkout@v2

    - name: Build and run Docker container
      run: |
        docker build -t mycontainer .
        docker run -v $(pwd)/output:/output mycontainer
        
    - name: Change permissions
      run: |
        sudo chmod -R 777 output/
        
    - name: Create artifact
      run: |
        cd output
        tar -cvzf result.tar.gz result.txt
        mv result.txt result.deb
      if: always()

    - name: Upload artifact
      uses: actions/upload-artifact@v2
      with:
        name: result-artifact
        path: output/result.tar.gz

docker.yml

name: Example Workflow

on: [push]

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
    - name: Checkout code
      uses: actions/checkout@v2

    - name: Build and run Docker container
      run: |
        docker build -t mycontainer .
        docker run -v $(pwd)/output:/output mycontainer

docker file

FROM debian

RUN apt-get update && apt-get install -y iproute2

RUN mkdir /output

CMD /bin/ss -tulpn > /output/result.txt

I tried to look for a solution on the Internet, but, alas, I came to a stupor, because I do not know how to solve the problem