golang Functional Options Pattern

golang Functional Options Pattern

package server

type Server {
  host string
  port int
  timeout time.Duration
  maxConn int
}

func New(options ...func(*Server)) *Server {
  svr := &Server{}
  for _, o := range options {
    o(svr)
  }
  return svr
}

func (s *Server) Start() error {
  // todo
}

func WithHost(host string) func(*Server) {
  return func(s *Server) {
    s.host = host
  }
}

func WithPort(port int) func(*Server) {
  return func(s *Server) {
    s.port = port
  }
}

func WithTimeout(timeout time.Duration) func(*Server) {
  return func(s *Server) {
    s.timeout = timeout
  }
}

func WithMaxConn(maxConn int) func(*Server) {
  return func(s *Server) {
    s.maxConn = maxConn
  }
}

 

package main

import (
  "log"
  
  "github.com/acme/pkg/server"
)

func main() {
  svr := server.New(
    server.WithHost("localhost"),
    server.WithPort(8080),
    server.WithTimeout(time.Minute),
    server.WithMaxConn(120),
  )
  if err := svr.Start(); err != nil {
    log.Fatal(err)
  }
}