func foo(r io.Reader) error {
    data, err := io.ReadAll(r)
    if err != nil {
        return err
    }
    _, err = fmt.Print(data)
}

Extracting the fmt.Print line to a function it becomes:

func foo(r io.Reader) error {
    data, err := io.ReadAll(r)
    if err != nil {
        return err
    }
    funcName(err, data)
}

func funcName(err error, data []byte) {
    _, err = fmt.Print(data)
}

GoLand thinks it has to add err as a parameter to funcName because the err variable is reused in foo, but we obviously don't want to pass the old err in as a parameter.