syntax for calling func that receive func as parameter

calling_func.go

package main

import "fmt"

func trace(requestName func() string) func(string) string {
	return func(text string) string {
		request := requestName()

		return fmt.Sprintf("operation: %s, request: %s", request, text)
	}
}

func main() {
	// first way to call the func trace()
	// it call func trace() to get s as a func() and then add parameter to s() in order to get the result
	s := trace(func() string {
		return "first way"
	})

	result := s("some param here")

	fmt.Println(result)

	// second way, it fullfil func trace() paramter followed by parameter needed in the return value (func) from func
	// trace. This might be usefull for some middleware such as http.Handler or else for trace or log something
	q := trace(func() string {
		return "second way"
	})("here is the paramter goes")

	fmt.Println(q)
}