Fix

The "error is not nil but has a nil value" error occurs because a Go interface variable holds a non-nil type (like an error) but its underlying value is nil, causing err != nil to be true while err.Error() panics. You must check both the interface and the underlying value to handle this correctly.

if err != nil {
    if err.Error() == "" {
        // Handle the nil-value case
        return
    }
    // Handle the actual error
    return err
}

Alternatively, if you control the function returning the error, ensure it returns nil instead of (*MyError)(nil). If you cannot change the source, use errors.Is or errors.As which handle this case safely, or explicitly check the concrete type if known.

The "error is not nil but has a nil value" issue happens when a variable is technically 'something' (not nil) but that 'something' is empty (nil value). It's like having a box labeled 'Error' that is empty inside; the box exists, so it's not missing, but there is nothing inside to read. You need to check if the box is empty before trying to read what's inside.