What is difference between Input Output (Request Response) since Easegress 2.0.0?

[jthann]

When upgrade Easegress from 1.x.x to 2.0.0，The are some protocol independent designs. For example in easegress/pkg/context/context.go These methods GetInputRequest GetOutputRequest GetInputResponse GetOutputResponse. In version 1.x.x，using Easegress as http gateway，These are only one request and response.
So what is difference between Input Output (Request Response) in Easegress 2.0.0 and how to understand its semantics and choose for future compatiblity?