Let's talk about how to use the log library to record logs in Go

In the Internet era, querying logs is a crucial task for programmers. In a complex system, there are thousands or even tens of thousands of lines of code that need to be maintained. Without a good logging system, front-end and back-end errors cannot be checked, and a lot of time and cost will be wasted. As a representative of modern languages, Golang naturally provides an excellent log query engine.

First of all, to implement log debugging and query in Golang, we need to use the standard library "Log", which provides some basic functions, such as writing logs, setting log levels, etc. Below I will briefly introduce how to use the log library to record logs in Go.

In Golang, we use the "log" of the standard library to record log information. With the following code, we can print out a hello world log on the console:

import "log"

func main() {
   log.Println("hello world")
}

This log is not particularly useful, so that we cannot perform any search or filtering on it. To make the logging more meaningful, we need to add some metadata to this, such as a timestamp and the name of the application, as shown below:

func main() {
  log.SetPrefix("golang-query-log")
  log.SetFlags(log.LstdFlags | log.Lshortfile)
  log.Println("hello world")
}

Now, we can see the following output on the console:

2021/02/21 16:40:39 golang-query-log main.go:21: hello world

We set the prefix to "golang-query-log" so that we know these logs are from our application and not the system logs. We also set the log flags to LstdFlags and Lshortfile, which adds the file name and line number to the log.

We can write logs to a file by using "bufio package" as shown below:

logfile, _ := os.OpenFile("log.txt", os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
defer logfile.Close()

log.SetOutput(logfile)
log.Println("hello world")

In this example, we create a file for "logfile" and pass "log .SetOutput" logs to this file. This means that, unlike the standard setup, our logs will not appear on the console, but will be written to the file "log.txt".

As our programs and applications become more complex, we can use learned techniques to record log levels, filter or search logs as needed, and perform other operations. Since logging has become easier in modern languages, we can spend more time actually solving problems instead of trying to find them.

Through the above introduction, I believe everyone already understands how Golang performs log query. Log query is a very important task. You must pay attention to the log settings in the code, and set the log level and output location appropriately to find the problem quickly and efficiently.

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