How to get the HTTP method in AWS Lambda?

API Gateway now has a built-in mapping template that passes along stuff like http method, route, and a lot more. I can't embed because I don't have enough points, but you get the idea.

Here is a screenshot of how you add it in the API Gateway console:

To get there navigate to AWS Console > API Gateway > (select a resource, IE - GET /home) > Integration Request > Mapping Templates > Then click on application/json and select Method Request Passthrough from dropdown shown in the screenshot above

The context.httpMethod approach works only in templates. So, if you want to have access to the HTTP method in your Lambda function, you need to find the method in the API Gateway (e.g. GET), go to the Integration Request section, click on Mapping Templates, and add a new mapping template for application/json. Then, select the application/json and select Mapping Template and in the edit box enter something like:

{
    "http_method": "$context.httpMethod"
}

Then, when your Lambda function is called, you should see a new attribute in the event passed in called http_method which contains the HTTP method used to invoke the function.