How do you make a function accept multiple types?

Starting with Go 1.18. you can use generics to specify which types can be used in a function.

func print_out_type[T any](x T) string {
    return fmt.Sprintf("%T", x)
}

https://go.dev/doc/tutorial/generics

You can use interface types as arguments, in which case you can call the function with any type that implements the given interface. In Go types automatically implement any interfaces if they have the interface's methods. So if you want to accept all possible types, you can use empty interface (interface{}) since all types implement that. No other modification needs to be done to your function.

func print_out_type(x interface{}) string {
    switch v := x.(type) {
        case string:
             return "A string"
        case int32:
             return "An Integer"
        default:
             return "A default"
    }
}

You can also use the reflect package to study the type of an interface variable. For Example:

func print_out_type(x interface{}) string {
    return reflect.TypeOf(x).String()
}

func main() {
    fmt.Println(print_out_type(42))
    fmt.Println(print_out_type("foo"))
}

Will print

int

string