How to write custom debug messages to a log file in Go?

To write custom debug messages to a log file in Go, you can use the standard library's log package. Below is an example of how you can set up a custom logger that writes debug messages to a log file:

Import the necessary packages:

import (
	"log"
	"os"
)

Set up a custom logger by defining a new logger with a custom log flag and output destination:

var (
	debugLogger *log.Logger
)

func InitLogger() {
	file, err := os.OpenFile("debug.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
	if err != nil {
		log.Fatal("Failed to open log file:", err)
	}

	debugLogger = log.New(file, "DEBUG: ", log.Ldate|log.Ltime|log.Lshortfile)
}

In the InitLogger() function, we create a new file debug.log (or open an existing one) to be used as the output destination for debug messages. Then, we initialize debugLogger with the file and set a custom log prefix using log.New().

Use the custom logger to write debug messages:

func main() {
	InitLogger()

	debugLogger.Println("This is a debug message")

	// ...
}

Now, when you run your Go application, any debug messages you write using debugLogger will be appended to the debug.log file with a timestamp and the relevant file and line number information.

Note: You can customize the log message format and file path as per your requirements.