Type Aliases are a reference to other types.

// TwitterHandler : type alias for twitterHandler
type TwitterHandler = string

// Person : Person struct
type Person struct {
	...
	twitterHandler TwitterHandler
}

Type Definition

// TwitterHandler : type definition for twitterHandler
type TwitterHandler string

Type Aliases copies the fields and the methods of a type to a new type,thereby becoming that exact type. We cannot extend and add new methods on them.

A Type Definition it only copies the fields of a type(underlying type) over to a new type, it does not copy the methods. We can add new methods. We have to use Explicit Type Conversion so it can access the method of the underlying type.

// TwitterHandler : type def for twitterHandler
type TwitterHandler string

// RedirectURL : RedirectURL
func (th TwitterHandler) RedirectURL() string {
	cleanHandler := strings.TrimPrefix(string(th), "@")
	return fmt.Sprintf("https://twitter.com/%s", cleanHandler)
}