Go Cookbook

Chapter 4. Logging Recipes

4.0 Introduction

Logging is the act of recording events that occur during the running of a program. It is often an undervalued activity in programming because it is additional work that has little immediate payback for the programmer.

During the normal operations of a program, logging is an overhead, taking up processing cycles to write to a file, database, or even to the screen. In addition, unmanaged logs can cause problems. The classic case of logfiles getting so big that they take up all the available disk space and crash the server is too real and happens too often.

However, when something happens, and you want to find out the sequence of events that led to it, logs become an invaluable diagnostic resource. Logs can also be monitored in real time, and alerts can be sent out when needed.

4.1 Writing to Logs

Problem

You want to log events that happen during the execution of your code.

Solution

Use the log package in the standard library to log events.

Discussion

Go provides a log package in the standard library that you can use to log events while the program is running. It has a default implementation that writes to standard error and adds a timestamp. This means you can use it out of the box for logging without configuration or setup if you’re looking to log to standard error.

The log package provides several functions that allow you to write logs. In particular, there are three sets of functions:

Print

Prints the logs to the logger