The import package not allowed error of test file

When I import native package into my test file.

// My cmd_test.go

package cmd_test

import (
    ...

    "github.com/myGithubProjectRootPath/internal"
)

...

It will always report use of internal package github.com/myGithubProjectRootPath/internal not allowed error. The cmd_test.go under cmd package directory.