用Golang撰寫Package的Best Practice

// .../services
package services

...

package main

func main() {}

const (
    StatusContinue           = 100 // RFC 7231, 6.2.1
    StatusSwitchingProtocols = 101 // RFC 7231, 6.2.2
    StatusProcessing         = 102 // RFC 2518, 10.1
    StatusEarlyHints         = 103 // RFC 8297

    StatusOK                   = 200 // RFC 7231, 6.3.1
    StatusCreated              = 201 // RFC 7231, 6.3.2
    StatusAccepted             = 202 // RFC 7231, 6.3.3
    StatusNonAuthoritativeInfo = 203 // RFC 7231, 6.3.4
    ...
)

var (
    // ErrNotSupported is returned by the Push method of Pusher
    // implementations to indicate that HTTP/2 Push support is not
    // available.
    ErrNotSupported = &ProtocolError{"feature not supported"}

    // Deprecated: ErrUnexpectedTrailer is no longer returned by
    // anything in the net/http package. Callers should not
    // compare errors against this variable.
    ErrUnexpectedTrailer = &ProtocolError{"trailer header without chunked transfer encoding"}
    ...
)

// A Client is an HTTP client. Its zero value (DefaultClient) is a usable client that uses DefaultTransport. ...
type Client struct {
    // Transport specifies the mechanism by which individual
    // HTTP requests are made.
    // If nil, DefaultTransport is used.
    Transport RoundTripper
    ...

// DefaultClient is the default Client and is used by Get, Head, and Post.
var DefaultClient = &Client{}

// CanonicalHeaderKey returns the canonical format of the header key s. The canonicalization converts the first letter and any letter following a hyphen to upper case; the rest are converted to lowercase. For example, the canonical key for "accept-encoding" is "Accept-Encoding". If s contains a space or invalid header field bytes, it is returned without modifications.

func CanonicalHeaderKey {...}

/*
 Package events provides a webservice that manages the libary's special events.
*/
package events

import (
	"fmt"
	"net/http"
	"strconv"

	"github.com/pluralsight/libmanager/services/internal/ports"
)

var port = 42

// StartServer registers the handlers and initiates the web service.
// The service is started on the local machine with the port specified by
// .../lm/services/internal/ports#EventService
func StartServer() error {
	sm := http.NewServeMux()
	sm.Handle("/", new(eventHandler))
	return http.ListenAndServe(":"+strconv.Itoa(port), sm)
}

func init() {
	fmt.Println("serve.go 1", port)
	port = ports.EventService
	fmt.Println("serve.go 2", port)
}

func init() {
	fmt.Println("second init in serve.go")
}

// Package main is typically used to define a single, executable command and its associated logic.
//
// Functions in the main package should normally avoid containing business logic; they
// should focus on initializing the application and handling any errors that are returned by
// any library calls.
package main

import (
	"fmt"
	"log"
	"sync"

	"github.com/pluralsight/libmanager/services/events"
)

func init() {
	fmt.Println("init in main.go")
}

// The main function, when defined in a main package, defines
// the entry and exit point for an executable command.
func main() {
	log.Println("Starting all services")

	// start the services
	wg := new(sync.WaitGroup)
	wg.Add(1)
  // 執行 events package內的StartServer方法
	go startServer(wg, events.StartServer)
	wg.Wait()
	log.Println("All services stopped")
}

// startServer is a function in the main package that supports the command.
func startServer(wg *sync.WaitGroup, startFunc func() error) {
	err := startFunc()
	wg.Done()
	if err != nil {
		log.Fatal(err)
	}
}

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by sa BSD-style
// license that can be found in the LICENSE file

// Package helloworld implements ....

package helloworld

package main

import "fmt"

func main() {
  fmt.Println("hello, gophers!")
}

package main

// 這時會引入了兩個叫做json的pakcage, compiler會出現混淆
import (
   "encoding/json"
   "pluralsight.com/libmanager/json"
)

func main() {
  ...
  data, err := json.Marshal(...)
}

import (
  "encode/json"
  lmjson "pluralsight.com/libmanager/json"
)

import (
  "database/sql"
  _ "github.com/lib/pq"
)

func init() {
	sql.Register("postgres", &Driver{})
}