The Go programming language has always had rich support for building REST APIs. This includes an excellent standard library (net/HTTP) along with many popular packages such as Gorilla mux, Gin, Negroni, Echo, Fiber, etc.
Using AWS Lambda Go runtime, you can use Go to build AWS Lambda functions. Imagine a web app that needs to authenticate users, store user data, and send emails. A Serverless approach for this would be to implement each functionality/API as a separate Lambda function. For example, you could have a Lambda function to handle user registration, another to handle user login, and so on.