structlog

Features

• log only key/value pairs
• output both as Text and JSON
• log level support
• compatible enough with log.Logger to use as drop-in replacement
• short names for service keys (like log level, time, etc.)
• support default values for keys
• service keys with caller's function name, file and line
• fixed log level width
• service key for high-level source name (like package or subsystem), caller's package name by default
• when creating new logger instance:
  • inherit default logger settings (configured in main())
  • add new default key/values
  • disable inherited default keys
• warn about imbalanced key/value pairs
• first parameter to log functions should be value for "message" service key
• able to output stack trace
• level-guards like IsDebug()
• output complex struct as key values (using "%v" like formatting)
• Error returns message as error (auto-convert from string, if needed)
  • actually it returns first .(error) arg if any or message otherwise
• convenient helpers IfFail and Recover for use with defer
• output can be redirected/intercepted
• when output as JSON:
  • add service field time by default
• when output as Text:
  • do not add service field time by default
  • order of keys in output is fixed, same as order of log function parameters
  • it is possible to set minimal width for some keys (both user and service ones)
  • it is possible to setup order for service keys, including this keys should be output before and after user keys
  • it is possible to choose output style for some keys: "key: ", "key=", do not output key name
  • it is possible to choose how to escape values by default and for selected keys: no escaping, use ``, use ""
  • do not support colored output - this can be added by external tools like grc and we anyway won't have colors in log files