I’m new to Go and a bit confused in how interfaces work when implemented, especially wrt. functions that have parameters. Say I have an interface with function foo that takes in an interface:

type I interface {
  foo(x interface{})
}

And a types A and B as below:

type A struct {
  // stuff
}
type B struct {
  // stuff
}

(a *A) foo(b B) {
 // do something
}

Since, in this example, A has method foo, is it considered to have implemented I, even with the specification of B as the param rather than a general interface? I have the same question for the function’s return types as well.

If not, how would one design an interface which allows a more general parameter/return type and for structs which implement it to specify the type?