How to get the directory of the package the file is in, not the current working directory

Question

I'm making a package to make API calls to a service.

I have a test package that I use just to test the API calls and test the functions of the main package which I just include the other package into.

In my main package that I'm working on I have

ioutil.ReadFile(filepath.Abs("Filename.pub"))

Which is ok, but when I call it from my test package e.g.

/Users/####/gocode/src/github.com/testfolder go run main.go

it tells me

panic: open /Users/####/gocode/src/github.com/testfolder/public.pub: no such file or directory

The problem is, is it is looking for public.pub inside of testfolder instead of github.com/apipackage/ which is where it is.

Just to clarify this mess of words:

The API Package has a function that reads from the same directory

But because I'm including the API package and Testfolder is the CWD when I go run main.go it is instead trying to get it from the testfolder instead even though the main.go doesn't have the function and is just including it.

Answer 1

runtime.Caller is what you want I believe.

Here is a demonstration :

package main

import (
    "fmt"
    "runtime"
    "path"
)

func main() {
    _, filename, _, ok := runtime.Caller(0)
    if !ok {
        panic("No caller information")
    }
    fmt.Printf("Filename : %q, Dir : %q\n", filename, path.Dir(filename))
}

https://play.golang.org/p/vVa2q-Er6D