interfaces with getters and setters in go language

I'm new to go language and having problems specifying an interface to a struct from different files with a getter and setter.

Source

src/github.com/user/interfaces

package interfaces

type IFoo interface {
	Name() string
	SetName(name string)
}

src/github.com/user/foo

package foo

import "github.com/user/interfaces"

type Foo struct {
	name string
}

func (f *interfaces.IFoo) SetName(name string) {
	f.name = name
}

func (f IFoo) Name() string {
	return f.name
}

If I change method signature of struct Foo to the following then the import "github.com/user/interfaces" becomes unused.

func (f *Foo) SetName(name string) {
	f.name = name
}

func (f Foo) Name() string {
	return f.name
}

Test

test/github.com/user/foo/foo_test.go

package foo

import (
	"testing"
	"github.com/user/foo"
	"fmt"
	"github.com/user/interfaces"
)

func TestFoo(t *testing.T) {
	foo := foo.Foo{}

	fmt.Println(interfaces.IFoo(foo))
}

Question: How can I specify the IFoo interface to the Foo struct and have the unit test pass in the above example?

> How can I specify the IFoo interface to the Foo struct

You don't. In Go, interface implementation is implicit. See https://tour.golang.org/methods/10.

Which is to say, if Foo implements all of the methods of the IFoo interface, it implements the interface. You don't need to "tell" the struct that it is an IFoo.

All you have to do is

func (f *Foo) SetName(name string) {
	f.name = name
}

func (f Foo) Name() string {
	return f.name
}

And then in your test you can do:

test/github.com/user/foo/foo_test.go

package foo

import (
    "testing"
    "fmt"
    "github.com/user/interfaces"
)

func TestFoo(t *testing.T) {
    var foo interfaces.IFoo = &Foo{}
    foo.SetName("bar")
    fmt.Println(foo.Name())
}

Edit: Your test file should live in the same folder as the file it is testing, you should not have them all in a test folder. That being said, if you want to keep the structure the same, you would need to make sure that your package name foo is not overwritten by your variable name foo, and then prefix Foo{} with foo:

test/github.com/user/foo/foo_test.go

package foo

import (
    "testing"
    "fmt"
    "github.com/user/interfaces"
    "github.com/user/foo"
)

func TestFoo(t *testing.T) {
    var f interfaces.IFoo = &foo.Foo{}
    f.SetName("bar")
    fmt.Println(f.Name())
}