Golang: gin: get base url

Question

I want to print base url of my routes, if you see my comments i mean the thing before colon sign : . More specifically its should be the thing before : sign of router.Run(":3000") here.

[ So according to my commented code it should be localhost. I just want to print localhost ]

package main

import (
    "fmt"
    "r/p/routes"

    "github.com/gin-contrib/cors"
    "github.com/gin-gonic/gin"
)

func main() {
    router := gin.Default()

    routes.X(router) // localhost:3000/getpens
    routes.Y(router) // localhost:3000/getpencils

    router.Use(cors.Default())
    fmt.Println("this is base path : "+router.BasePath())
    router.Run(":3000")
}

So here X and Y are two functions that return routes from routes package, my api is fine, response ok tested by postman. I just want to print the string before : sign

In my attempts, I tried using router.BasePath() . But that only prints /

So please help me to do this