How to use log levels to control the verbosity of log output in Go?

In Go, log levels are not built-in, but you can define your own log levels and use them to control the verbosity of log output. Here's a step-by-step guide on how to accomplish this:

Define log levels: Create a new type to represent the different log levels. You can use the int type with iota to assign integer values to each log level. For example:

type LogLevel int

const (
    Debug LogLevel = iota
    Info
    Warning
    Error
)

Create a logger: Use the log package's New() method to create a logger instance. This will allow you to specify the output destination, such as standard output or a file. For example:

logger := log.New(os.Stdout, "", log.LstdFlags)

Define log level check function: Create a helper function that checks if the log message's level is higher than the currently set log level. This function will be used to determine whether to output the log message or not. For example:

func isLogLevelEnabled(currentLevel, logLevel LogLevel) bool {
    return logLevel >= currentLevel
}

Use log levels in your code: When logging messages, check if the log level is enabled using the isLogLevelEnabled() function. If the log level is enabled, output the log message using the logger. For example:

func LogMessage(currentLevel, logLevel LogLevel, message string) {
    if isLogLevelEnabled(currentLevel, logLevel) {
        logger.Println(message)
    }
}

Set the current log level: In your code, set the current log level to the desired level. This can be done programmatically based on a configuration file, environment variable, or command-line argument. For example:

currentLevel := Info // Set log level to 'Info'

LogMessage(currentLevel, Debug, "This is a debug message")
LogMessage(currentLevel, Info, "This is an info message")
LogMessage(currentLevel, Warning, "This is a warning message")
LogMessage(currentLevel, Error, "This is an error message")

By using log levels to control the verbosity of log output, you can easily adjust the amount of information that is logged based on your needs.