Golang中的字符串和通用函数的映射

I'm trying to create a map that will map strings to functions. Not all functions have the same signature. For example, I'd like to have something like this:

rf := map[string]func(...interface{}) error{
    "FirstName":        validateExistence(a.FirstName, "FirstName is required."),
    "Postcode":         validateMatchPattern(a.Postcode, `^\d{5}$`, "Could not match pattern for postcode."),
    "Address":          validateLength(a.Address, 0, 35, "Address must have up to 35 chars."),
}

I'm getting this error:

cannot use validateExistence("FirstName is required.") (type func(string) error) as type func(...interface {}) error in map value

map[string]func(f string, m string) errorFirstName

cannot use validateMatchPattern(a.Postcode, "^\\d{5}$", "Could not match pattern for postcode.") (type error) as type func(string) error in map value
cannot use validateLength(a.Address, 0, 35, "Address must have up to 35 chars.") (type error) as type func(string) error in map value

func(...interface{})

So, my question is: is there any other way to declare the map that can hold functions with different signatures?