How Can I Get the Correct Package Directory in Go When Using `ioutil.ReadFile()` in Tests?

Getting the Package Directory in Go

You're facing an issue where ioutil.ReadFile() is trying to locate a file in the wrong directory when you call it from a test package. The problem boils down to how the current working directory (CWD) is determined in your setup.

To resolve this, the solution lies in using runtime.Caller(). This function provides information about the caller of the current function. By using the file path returned by runtime.Caller(), you can derive the directory of the package where the file is located.

Here's an example that demonstrates how to use runtime.Caller():

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))
}

When this code is executed, it will print the filename and directory of the file that called it. This allows you to accurately locate files regardless of the CWD.

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