如何在Go中编写一个同时接受字符串和int64类型的函数？

I have function that looks like this

func GetMessage(id string, by string) error {
    // mysql query goes here
}

I have message_id which is string and id which is primary key.

I would like to accept both types for id parameter.

I have tried like this

if (by == "id") {
        int_id, err := strconv.ParseInt(id, 10, 64)
        if err != nil {
            panic(err)
        }
        id = int_id
    }

But I'm getting error like

cannot use int_id (type int64) as type string in assignment

can someone help me?

Thanks

Use interface{} like this working sample:

package main

import "fmt"
import "errors"

func GetMessage(id interface{}) error {
    //fmt.Printf("v:%v\tT: %[1]T 
", id)
    switch v := id.(type) {
    case string:
        fmt.Println("Hello " + v)
    case int64:
        fmt.Println(v + 101)
    default:
        //panic("Unknown type: id.")
        return errors.New("Unknown type: id.")
    }
    return nil
}

func main() {
    message_id := "World"
    id := int64(101)
    GetMessage(message_id)
    GetMessage(id)
}

output:

Hello World
202