如何在go包中使用常量

Question

I'm writing my first go code and I'm trying to convince myself what I'm doing is not wrong.

anyway, here the project the tree structure.

.
├── helpers
│   └── common.go
├── logger
│   └── util.go
├── logger_example
└── runner.go

The main file to look over here is logger/util.go which look like this.

package logger

import (
  "log"
  "os"
)

type Logger struct {
  *log.Logger
}

func (l *Logger) Info(v ...interface{}) {
  l.SetPrefix("Info: ")
  l.Println(v...)
}

func (l *Logger) Error(v ...interface{}) {
  l.SetPrefix("Error: ")
  l.Println(v...)
}

func (l *Logger) Warn(v ...interface{}) {
  l.SetPrefix("Warn: ")
  l.Println(v...)
}

func (l *Logger) Debug(v ...interface{}) {
  l.SetPrefix("Debug: ")
  l.Println(v...)
}



func NewLogger() *Logger {
  logger := log.New(os.Stdout, "", log.Ldate|log.Ltime|log.Lshortfile)
  return &Logger{logger}
}

As you all can see, I'm just setting the prefix to "INFO | WARN | ERROR | DEBUG"

On the main package I have safely created a Logger instance and VOILA it worked.

Only until I decided to add a helpers package and now things do not look the way I wanted.

since the logger.Logger instance created inside main package, I have to pass it reference to every since package function where I want to invoke the logger statement. (see the below example ..)

// dodly_logger/logger/common.go
package helpers

import "dodly_logger/logger"
func Display(dodlyLogger *logger.Logger) {
  dodlyLogger.Info("Inside a helper package")
}

The Main package..

package main

import (
  logger "dodly_logger/logger"
  helpers "dodly_logger/helpers"
)

func main() {
  dodlyLogger := logger.NewLogger()
  dodlyLogger.Info("INFO MESSAGE")
  dodlyLogger.Error("ERROR MESSAGE")
  // Ehh, I have to pass the dodlyLogger ..
  helpers.Display(dodlyLogger)
}

Ok, now I know my GOLang knowledge is not complete hence I'm hoping people over here can point me how can I write this more clinically wherein I do not have to pass the reference of the logger.Logger to every function for which I need to log.

Answer 1

Create a package level variable with var.

package main

import (
    logger "dodly_logger/logger"
    helpers "dodly_logger/helpers"
)

var dlogger logger.Logger

func init() {
    dlogger = logger.NewLogger()
}

func main() {
    dlogger.Info("Starting Main")
    a()
}

func a() {
    dlogger.Info("in a")
}