This conversion tool was inspired by my recent review of Google's alpha-release of Cloud Functions: Google Cloud Functions VS AWS Lambda: fight for serverless cloud domination begins.
Install rewrite-js as follows:
npm install -g rewrite-js
You can generate the Google Functions output - given your AWS Lambda function input - as follows:
cat lambda_function.js | rewrite-js awslambda2googlefunctions.js > google_function.js
You can have a look at some examples here.
This tool is only supposed to speed the function porting process up. It won't take care of resolving unpredictable naming conflicts, testing or deploying your new Google function.