start-task.yaml

apiVersion: tekton.dev/v1alpha1
kind: Task
metadata:
  name: read-task
spec:
  inputs:
    params:
    - name: FILENAME
    resources:
    - name: source
      type: git
  steps:
  - name: read-file-content
    image: ubuntu
    script: 'cat $(inputs.resources.source.path)/$(inputs.params.FILENAME)'
    

1. start taskrun using using tkn-cli

 tkn task start read-task -i=source=my-resource -p=FILENAME=docs/README.md