Golang is an efficient programming language that is superior to other languages ​​in many ways. Logging is a critical task when it comes to recording the behavior of your application. In Golang, logging is crucial for debugging and testing applications.

This article will introduce the method of logging in Golang. We will discuss loggers in the standard library as well as third-party libraries.

Use the standard library to record logs

Golang's standard library has a package called "log", which provides a simple logging method. This package provides three levels of logging: Info, Warning, and Error.

First you need to import the logger:

import "log"

1. Record information

Record information by calling the "log.Println()" function. It logs a message to standard error output.

log.Println("Record this info")

This code will output information similar to the following:

2019/11/22 20:04:14 Record this info

2. Logging warnings

Log warnings by calling the "log.Println()" function . It logs a warning to standard error and prepends "WARN" to the message.

log.Println("WARN: Warning message here")

This code will output information similar to the following:

2019/11/22 20:05:20 WARN: Warning message here

3. Logging errors

Log errors by calling the "log.Println()" function . It logs an error to standard error and prepends "ERROR" to the message.

log.Panicln("ERROR: error message here")

This code will output information similar to the following:

2019/11/22 20:06:28 ERROR: error message here
panic: ERROR: error message here

goroutine 1 [running]:
log.Panicln(0xc42000e170, 0x1, 0x1)
        /usr/local/go/src/log/log.go:341 +0xc4
main.main()
        /root/go/src/main.go:10 +0x55
exit status 2

The above code will cause the program to panic. When an error occurs, the program will terminate immediately after logging the error and output detailed error information.

Using third-party libraries for logging

The logging functions provided by the standard library have their limitations. You can use third-party libraries to extend logging capabilities. Since third-party logging libraries provide rich features, they are more practical for application debugging and testing.

Here we take the "go-logging" class library as an example. It can record multiple log levels (Info, Warning, Error and Debug).

First install "go-logging":

go get github.com/op/go-logging

Import library:

import (
     "github.com/op/go-logging"
     "os"
)

1. Initialize the logger

Use " logging.MustGetLogger()" function to initialize the logger. You can optionally specify a name as a parameter to identify it between multiple loggers.

var log = logging.MustGetLogger("example")

2. Set the log level

After initializing the logger, you can use the "log.SetLevel()" function to set the log level. This function accepts a parameter of type logging.Level (including Debug, Info, Warning and Error).

logging.SetLevel(logging.DEBUG, "example")

3. Create a file logger

Create a file logger by using the "os.Create()" function:

logFile, err := os.Create("app.log")
if err != nil {
     log.Error("Cannot create log file", err)
}
defer logFile.Close()

4. Create Formatter

Create a formatter for formatting log file entries:

formatter := logging.MustStringFormatter(
"%{time:2006/01/02 15:04:05.000} %{shortfile} %{level:.6s} %{message}")

5. Configuring the file logger

Pass " logging.NewBackendFormatter()" function creates a file logger:

backend := logging.NewBackendFormatter(
 logging.NewLogBackend(logFile, "", 0),
 formatter)

6. Add the file logger to the logger

You need to record the file before adding the file logger Wrap the logger into a backend:

logging.SetBackend(backend)

Or add multiple loggers:

logging.SetBackend(logging.MultiLogger(
     logging.MultiWriter(os.Stdout, logFile),
     logging.MultiWriter(os.Stderr, logFile),
))

7. Logging

Now you can use the logger via Level to "record" log information:

log.Infof("This is a info message with %d", 123)
log.Warningf("This is a warning message with %s", "param")
log.Errorf("This is a error message with %v", err)

The above code will format the log when recording it, and then write it to the log file.

Summary:

Golang’s standard library provides a simple logging method. However, using a third-party library gives you greater control over the logger's behavior and format. By using the "logging" library you can log multiple log levels and write them to a file.

The above is the detailed content of How to log in golang. For more information, please follow other related articles on the PHP Chinese website!