How to solve circular dependency without creating new package?

Question

In golang want a plugins system with a global registry. Structure can be simplified as follows:

/plugins/registry.go
/plugins/plugin1/impl.go

registry.go:

package plugins

import "plugins/plugin1" // required for plugin1.MakePlugin

type IPlugin interface {
  Register() error
}

type Factory func(x int) IPlugin

var registry = []Factory{
  plugin1.MakePlugin,
}

impl.go:

package plugin1

import "plugins" // required for IPlugin

type Plugin struct {
  x int
}

func MakePlugin(x int) plugins.IPlugin {
  return &Plugin{
    x: x,
  }
}

How to solve without moving IPlugin to 3rd (e.g common) package?

PS. I thought if i return *Plugin from MakePlugin this will be compatible with Factory, but its not!!!

Answer 1

Try to separate the Interfaces from their implementation to external packages that are abstract. Then, depend on them according to the Dependency injection and Adapter pattern paradigms.