Import and reuse existing struct from different package

I need to import the existing struct from different package that lives in vendor folder. My folder stucture is below

       projectname
           custom
              custom.go
           vendor
              github.com
                somepackage
                   authentication
                    models.go

the models.go contains this struct

package authentication

type User struct {
        ID           int64
        AccessToken  string
        Email        string
        FullName     string
        Password     string
        PasswordHash string
        PasswordSalt string
        Readonly     bool
        Role         Role
        Token        string
        Username     string
}

Now inside my custom/custom.go, I have a function that follows a signature and the code looks like this

Signature

type loginFn func(string, string) (*User, error)

I import like this

import "github.com/somepackage/authentication/models"

func SetupGoGuardian(u, p string) (*User, error) {

But I got error coud not import ...... (no required module provides package)

How to properly import the struct from another package and use it a custom function?

You cannot import files, only packages. Change your import statement to reference the package name:

import "github.com/somepackage/authentication"