packaging - Registering packages in Go without cyclic dependency

Question

I have a central package that provides several interfaces that other packages are dependent on (let us call one Client). Those other packages, provide several implementations of those first interfaces (UDPClient, TCPClient). I instantiate a Client by calling NewClient in the central package, and it selects and invokes the appropriate client implementation from one of the dependent packages.

This falls apart when I want to tell the central package about those other packages, so it knows what clients it can create. Those dependent client implementations also import the central package, creating a cyclic dependency which Go does not allow.

What's the best way forward? I'd prefer not to mash all those implementations in a single package, and creating a separate registry package seems overkill. Currently I have each implementation register itself with the central package, but this requires that the user knows to import every implementation in every separate binary that makes use of client.

import (
    _ udpclient
    _ tcpclient
    client
)

Answer 1

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