Golang higher-order functions use Functional Options

`package main

import ( “crypto/tls” “fmt” “time” )

// Business entity

type Server struct { Addr string Port int Protocol string Timeout time.Duration MaxConns int TLS *tls.Config }

// Higher order function

type Option func(*Server)

func Protocol(p string) Option { return func(server *Server) { server.Protocol = p } }

func Timeout(timeout time.Duration) Option { return func(server *Server) { server.Timeout = timeout } }

func MaxConns(maxconns int) Option { return func(server *Server) { server.MaxConns = maxconns } }

func TLS(tls *tls.Config) Option { return func(server *Server) { server.TLS = tls } }

func NewServer(addr string, port int, options … func(*Server)) (*Server, error) { serv := Server{ Addr: addr, Port: port, Protocol: “tcp”, Timeout: 30 * time.Second, MaxConns: 1000, TLS: nil, }

for _, option := range options {
    option(&serv)
}
return &serv, nil
Copy the code

}

Func main() {server, _ := NewServer(“127.0.0.1”, 9999, Protocol(“UDP”), MaxConns(100)) fmt.Println(server.Protocol) fmt.Println(server.MaxConns) }`