在Golang函数中使用默认值

Question

I'm trying to implement a default value according to the option 1 of the post Golang and default values. But when I try to do go install the following error pops up in the terminal:

not enough arguments in call to test.Concat1
    have ()
    want (string)

Code:

package test

func Concat1(a string) string {
  if a == "" {
    a = "default-a"
  }
  return fmt.Sprintf("%s", a)
}

// other package

package main

func main() {
  test.Concat1()
}

Thanks in advance.

Answer 1

I don't think what you are trying to do will work that way. You may want to opt for option #4 from the page you cited, which uses variadic variables. In your case looks to me like you want just a string, so it'd be something like this:

func Concat1(a ...string) string {
  if len(a) == 0 {
    return "a-default"
  }
  return a[0]
}