README.md

structlog

Structured logger for Go using the message templates format. Inspired by Serilog.

Motivation

Structured logging makes it easier to search and extract useful information from your logs. In Go this usually means passing key-value pairs to your logger in addition to a string message. This library takes a more compact approach by embeddeding key names in the format string itself.

Example

import (
    "github.com/danstiner/structlog"
    "github.com/danstiner/structlog/sink"
)

type Coordinates struct {
    Latitude, Longitude float64
}

log := structlog.New(sink.Json{os.Stdout})

log.Info("Processed {@position} in {elapsed} ms", Coordinates{25, 132}, 34)

Formatted output:

{
  "$level":"INFO",
  "$message":"Processed {\"Latitude\":25,\"Longitude\":132} in 34 ms",
  "$template":"Processed {@position} in {elapsed} ms",
  "$timestamp":"2228-03-22T12:34:56Z",
  "elapsed":34,
  "position":{"Latitude":25,"Longitude":132}
}

Some benefits of this approach:

• Simple syntax, just surround key names in the format with braces and put the values in the same order
• @ can be used to serialize structs and other complex values as JSON
• The format string can be logged as is, this makes it easy to use grep to find which line of code a log came from

Interface

type Logger struct {
    Trace(template string, values ...interface{})
    Info(template string, values ...interface{})
    Error(template string, values ...interface{})
    Panic(template string, values ...interface{})

    With(key string, value interface{}) Logger
    WithFields(fields Fields) Logger
    WithError(err error) Logger
}

type Fields map[string]interface{}