https://jordanorelli.com/post/32665860244/how-to-use-interfaces-in-go

Interfaces allow us to define a type by what it can do rather than what it is.

type Animal interface {
  Speak() string
}

In this example and Animal is anything that can Speak(). Here's some types that satisfy this interface.

type Dog struct {
}

func (d Dog) Speak() string {
  return "Woof!"
}

type Cat struct {
}

func (c Cat) Speak() string {
  return "Meow!"
}

type Llama struct {
}

func (l Llama) Speak() string {
  return "?????"
}

Now we could throw these in a slice and see what each animal says:

func main() {
  animals := []Animal{Dog{}, Cat{}, Llama{}, JavaProgrammer{}}
  for _, animal := range animals {
    fmt.Println(animal.Speak())
  }
}

This article describes an idiomatic approach to using channels inside interfaces:
https://kdsch.org/post/clean-concurrency-go/