public T getRequest() {
        return request;
    }
A context object that is created at start of each load balancer execution
and contains certain meta data of the load balancer and mutable state data of 
execution per listener per request. Each listener will get its own context
to work with. But it can also call {@link ExecutionContext#getGlobalContext()} to
get the shared context between all listeners.

@author Allen Wang
ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer/reactive/ExecutionContext.java