Function register_backend 

pub fn register_backend(backend: impl RegisterBackend + Send + Sync + 'static)

Registers a backend implementation for use with nyquest.

This function should be called once at the beginning of a program to set up the backend that will be used by all nyquest client operations.

Backend developers should create a type that implements:

• AsyncBackend trait if the async feature is enabled
• BlockingBackend trait if the blocking feature is enabled

Panics

Panics if a backend has already been registered.