Logging in Golang

Logging is important.
Logging is really important.
Always be logging.

Using the log Package

Official docs here

The log package defines the Logger type.
This type has methods for formatting output.

The output functions have the same variations.

• log.Print: The base function.
• log.Printf: The format string variation.
• log.Println: The newline variation.

The same goes for:

• log.Fatal[f|ln]
• log.Panic[f|ln]

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The Fatal functions call os.Exit(1) after writing the log message. The Panic functions call panic() after writing the log message.

Creating a Logger

Create a new logger with log.New.

func New(out io.Writer, prefix string, flag int) *Logger

Logger Methods

log.SetOutput

SetOutput sets the output destination for the standard logger. It takes an io.Writer as an argument.

You can also call log.Writer to get the current output destination.

log.SetPrefix

SetPrefix sets the output prefix for the standard logger.
i.e., the prefix is prepended to each log message.

log.Print[f|ln]

Print calls Output to print to the standard logger.

Printf and Println do the same. They handle arguments just like fmt.Printf/fmt.Println.

log.Fatal

log.Fatal is equivalent to Print followed by a call to os.Exit(1).