Read file from relative path with different callers - go

Question

I'm trying to read from a file in my project's directory.
My problem is, that depending on the caller, the path changes. The caller changes, because I want to unit test this code and the caller is not Main.go anymore.
This is what my project structure looks like:
The code where I try to access specialChars.txt from looks like this:
func RemoveSpecialChars(word string) string {
file, err := ioutil.ReadFile("wordlists/specialChars.txt")
[...]
}
This code works for the start from Main.go but not for the start from CleanupUtil_test.go. To get it working from the test I would need file, err := ioutil.ReadFile("../wordlists/specialChars.txt")
I found answers like this one: https://stackoverflow.com/a/32163888/2837489
_, filename, _, ok := runtime.Caller(0) which is obviously also dependent on the caller.
Is it possible to get the projects root path independent of the calling function?
Or is my code design wrong? Should I pass the file path into the function?

Answer 1

Starting from Go 1.16, you can use the embed package. This allows you to embed the files in the running go program. It comes with the caveat that the referenced directory needs to exist at or below the embedding file. In your case, the structure would look as follows:
-- main.go
-- cleanup
-- wordlist
\- specialChars.txt
CleanupUtil.go
CleanupUtil_test.go
You can reference the file using a go directive
// CleanupUtil.go
package cleanup
import (
"embed"
)
//go:embed wordlists/specialChars.txt
var content embed.FS
func RemoveSpecialChars(word string) string {
file, err := content.ReadFile("wordlists/specialChars.txt")
[...]
}
This program will run successfully regardless of where the program is executed. You should be able to reference this code in both your main.go file and your CleanupUtil_test.go file.

Answer 2

Pass in the filepath as a parameter to the function (as indicated in your last question).
More details:
The relative path "wordlists/specialChars.txt" is in fact not dependent on where the source file is located (such as Main.go or CleanupUtil_test.go), but where you execute it from. So you could run your tests from your root directory and then it would actually work. In short, the current working directory is relevant.
Still, I'd recommend specifying the path, because that makes your function more reusable and universal.
Maybe you don't even need to put this information into a file, but can simply have a string containing those chars. In this case you could also check if https://golang.org/pkg/regexp/#Regexp.ReplaceAll already covers your use case.