Quick Start

This page constructs a logger, logs at each level, and reads the output in both console and JSON form.

Construct a logger

srog.New builds an immutable, concurrency-safe *Logger from functional options. With no sink option it defaults to a single JSON sink on os.Stdout at Information level. srog.MustNew panics instead of returning an error — safe for configurations without file sinks.

log, err := srog.New(srog.WithConsole())   // colorized console on stdout
log := srog.MustNew()                      // JSON to stdout, Information level
log := srog.NewConsole()                   // dev preset: console, Debug level, stack traces

Call log.Close() on shutdown when file, async, or network sinks are configured; it releases file handles, drains async queues, and flushes/closes writers that came from registered sink types (such as the otlp sink).

Log at each level

Level methods take a message template followed by the arguments that fill its holes, in order. Error and Fatal additionally take the triggering error as their first argument (pass nil if there is none).

log := srog.MustNew(
	srog.WithConsole(srog.NoColor()),
	srog.WithLevel(srog.DebugLevel),
)
defer log.Close()

log.Debug("evaluating {Candidates} drivers near {Zone}", 14, "downtown-east")
log.Information("trip {TripId} assigned to driver {DriverId} eta {EtaSeconds}s", "T-58201", "D-107", 240)
log.Warning("surge multiplier {Multiplier} exceeds cap in {Zone}", 3.1, "airport")
log.Error(errors.New("driver socket closed"), "lost contact with driver {DriverId}", "D-107")

Console vs JSON

The same four calls, through a console sink and through the default JSON sink:

Console

2026-07-13T11:55:30+03:00 DBG evaluating 14 drivers near downtown-east
2026-07-13T11:55:30+03:00 INF trip T-58201 assigned to driver D-107 eta 240s
2026-07-13T11:55:30+03:00 WRN surge multiplier 3.1 exceeds cap in airport
2026-07-13T11:55:30+03:00 ERR lost contact with driver D-107 driver socket closed

JSON

{"level":"debug","@mt":"evaluating {Candidates} drivers near {Zone}","Candidates":14,"Zone":"downtown-east","time":"2026-07-13T11:55:30+03:00","message":"evaluating 14 drivers near downtown-east"}
{"level":"info","@mt":"trip {TripId} assigned to driver {DriverId} eta {EtaSeconds}s","TripId":"T-58201","DriverId":"D-107","EtaSeconds":240,"time":"2026-07-13T11:55:30+03:00","message":"trip T-58201 assigned to driver D-107 eta 240s"}
{"level":"warn","@mt":"surge multiplier {Multiplier} exceeds cap in {Zone}","Multiplier":3.1,"Zone":"airport","time":"2026-07-13T11:55:30+03:00","message":"surge multiplier 3.1 exceeds cap in airport"}
{"level":"error","error":"driver socket closed","@mt":"lost contact with driver {DriverId}","DriverId":"D-107","time":"2026-07-13T11:55:30+03:00","message":"lost contact with driver D-107"}

Reading the JSON shape:

Field	Meaning
level	zerolog level name (debug, info, warn, error, ...)
@mt	the raw message template — always present, groups events by template identity
Candidates, Zone, ...	typed structured fields bound from the template holes
error	attached error text (from Error/Fatal)
time	timestamp (RFC 3339 by default; configurable via WithTimeFormat)
message	the rendered human-readable message (omit with WithRenderedMessage(false))

The console format deliberately shows only the timestamp, level, rendered message, error, and caller — structured parameters stay in the JSON sinks.

INFO

Console output is colorized by default (ANSI codes). The captures above use srog.NoColor(); in a terminal you get colored level tags and a dimmed timestamp.

Both at once

A logger fans out to any number of sinks, each with its own format and level — the most common production setup is a pretty console plus a JSON file:

log, err := srog.New(
	srog.WithConsole(srog.MinLevel(srog.DebugLevel)),
	srog.WithFile("/var/log/app.log", srog.MinLevel(srog.InformationLevel)),
)
if err != nil {
	panic(err)
}
defer log.Close()

Continue with Message Templates for the full template syntax, or Sinks for everything about outputs.