Update README example for accessing headers

[mehyedes]

Updated README example for accessing the headers with the python3-http template

Signed-off-by: Mehdi Yedes mehdi.yedes@gmail.com

Description

Motivation and Context

Using event.headers['Some-Header'] throws an error when calling a python3-http function if the header is not set. So it is better to use event.headers.get('Some-Header') instead.

How Has This Been Tested?

After deploying this small function

def handle(event, context):
    header = event.headers.get('Test-Header')
    return {
        "statusCode": 200,
        "body": {
            "Header received": header
        }
    }

The function would not fail, but only return null when the header Test-Header is not set

$ curl 127.0.0.1:8080/function/python-test -H "Test-Header: testtest"
{"Header received":"testtest"}

$ curl 127.0.0.1:8080/function/python-test 
{"Header received":null}

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [ ] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I've read the CONTRIBUTION guide
• [x] I have signed-off my commits with git commit -s
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.