A msg.Format is any function that can format and print a log message. The format package includes a few of these, described below.
Flat is the default log format, and prints a single line of text which includes the message, timestamp, name of the logger or the current function, fields, and the message text. This format is a good place to start for most long-running applications.
JSON prints each log as a JSON object, making them easier to parse and analyze at scale. This format is useful if you plan to use tools like the Elastic Stack to monitor your application's activity.
This minimalist log format ignores the timestamp and current function name. This is useful for small command-line tools that need to print messages without too much ceremony.
