We are converting AWS Lambdas from Java due to excessive cold start times. Usage: These lambdas handle XML and JSON payloads, they use s3, API Gateway, RDS, DynamoDB, and external API's. Most of our developers are only experienced in java. These three languages (Go, Node.js, and Python) were discussed, but no consensus has been reached yet.
If you want to prioritise language familiarity, JavaScript is more like Java than the other choices; and it can be optimised to run very fast. However if you need really fast cold-start times, you can't beat Go since it's compiled. There are other things to consider, such as the massive amount of community packages and help/documentation in the JavaScript ecosystem. Go is newer but seems to be quite popular if you need something that runs fast in a single binary.
I've worked with all three of these languages and also with Java developers converting to these languages and far and away Go is the easier one to convert to. With the improved cold-start times and the ease of conversion for a Java developer, it is a no-brainer for me.
The hardest part of the conversion though is going to be the lack of traditional Classes so you have to be mindful of that, but Go Structs and interfaces tend to make up for what is lost there.
Full Disclosure: I'm a 95% Go convert (from Python) at this point in time.
