I have created a simple costume logger to print the error log and save it to a file with specific location.

package logger

import (
    "log"
    "os"
)

var trace *log.Logger
var filePathVar string
var fileNameVar string
var prefixVar string

// use this function first before calling others.
func InitLogger(prefix, filePath, fileName string) {
    setPrefix(prefix)
    createLogFile(prefix, filePath, fileName)
    filePathVar = filePath
    fileNameVar = fileName
    prefixVar = prefix
}

func setPrefix(prefix string) {
    trace = log.New(os.Stderr,
        prefix,
        log.Ldate|log.Ltime|log.Lshortfile)

}

func createLogFile(prefix, filePath, fileName string) (*os.File, error) {
    setPrefix(prefix)
    f, err := os.OpenFile(filePath+fileName, os.O_RDWR|os.O_CREATE|os.O_APPEND, os.ModePerm)
    if err != nil {
        // error file is not created
        err = os.MkdirAll(filePath, os.ModePerm)
        if err != nil {
            trace.Println(err)
            return nil, err
        }
        createLogFile(prefix, filePath, fileName)
    }

    return f, nil
}

// use this PrintLog use print the error on the terminal without exitting apps.
func PrintLog(errorLog string) {
    //assign to global variable
    if filePathVar == "" || fileNameVar == "" || prefixVar == "" {
        trace.Fatalln("Error file path and Name empty prefix Cannot be Empty")
    }

    f, err := createLogFile(prefixVar, filePathVar, fileNameVar)
    if err != nil {
        trace.Fatalln(err)
        return
    }
    trace.Println(errorLog)
    // save the log out put to file
    trace.SetOutput(f)
    trace.Println(errorLog, err)
}

// use this Fatal log to exit the application whenever got error.
func FatalLog(errorLog string) {
    //assign to global variable
    if filePathVar == "" || fileNameVar == "" || prefixVar == "" {
        trace.Fatalln("Error file path and Name empty")
    }

    f, err := createLogFile(prefixVar, filePathVar, fileNameVar)
    if err != nil {
        trace.Fatalln(err)
        return
    }
    trace.Println(errorLog)
    // save the log out put to file
    trace.SetOutput(f)
    trace.Fatalln(errorLog, err)
}

To use this package I must call the InitLogger function first

logger.InitLogger("Prefix Logger","./filpath/","filename.txt")

And then after that I can choose to print the error using either PrintLog or FatalLog.

The PrintLog function is used when we wanted to print the log without having crashing or closing the app os.Exit. The FatalLog the same as PrintLog but will crash the app or called os.Exit.

Any idea what can be improved here? source code