如何在Go中将包分配给变量？

Question

First of all, the word "variable" might be wrong in the question but I assume the detailed question explains why I'm using the word "variable".

I have two packages with different names but the exact same function(s).

Depending on the input of the user I want to use the function of a package. But instead of switching over the packages I would like to assign the package to a new function with a generic name, how to do this? And if it's not possible, why?

// foo/bar.go

package foo

func Test() {
    fmt.Println("hola from bar")
}

---

// baz/bar.go

package baz

func Test() {
    fmt.Println("hola from baz")
}

---

// main.go

package main

import (
    "foo"
    "baz"
)

func main() {

    thePackage := flag.String("package", "foo", "a package")

    if thePackage == "foo" {
        howToSetThis := foo // How to do this?
    } else {
        howToSetThis := baz // How to do this?
    }

    howToSetThis.Test() // execs Println from one of the two bar.go files

}

In JavaScript I would do something like (simplified):

function foo(){
  console.log("hola from foo")
}

function baz(){
  console.log("hola from baz")
}

if(somethingInput == "foo"){
  var howToSetThis = foo;
} else {
  var howToSetThis = baz;
}

howToSetThis();

Answer 1

You could define a interface in a package that requires the functions you want to have in those two packages .

package intfc

type Intfc interface {
    Test()
}

And then two structs in different packages which implements that interface

package foo

import "fmt"

type Foo struct {

}

func (f Foo) Test() {
    fmt.Println("hola from foo")
}

and

package baz

import "fmt"

type Baz struct {

}

func (f Baz) Test() {
    fmt.Println("hola from baz")
}

And then in main do something like this:

package main

import (
    "foo"
    "baz"
    "intfc"
    "flag"
)

func main() {

    var howToSetThis intfc.Intfc

    thePackage := flag.String("package", "foo", "a package")

    if *thePackage == "foo" {
        howToSetThis = foo.Foo{}
    } else {
        howToSetThis = baz.Baz{}
    }

    howToSetThis.Test() // execs Println from one of the two bar.go files

}