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Answer: log/slog, added in Go 1.21, brings structured logging to the standard library.

Quick start

import "log/slog"

slog.Info("hello, world", "user", "jba")

logger := slog.New(slog.NewJSONHandler(os.Stdout, nil))
logger.Warn("slow request", "path", "/api", "ms", 812)

JSON output looks like {"time":"...","level":"INFO","msg":"hello, world","user":"jba"}.

Concepts

• Levels: Debug, Info, Warn, Error.
• For more control over the output format, create a logger with a different handler. (S2)

Claims

• id: C1 claim: log/slog in Go 1.21 brings structured logging to the standard library. source: S1 evidence: "The new log/slog package in Go 1.21 brings structured logging to the standard"
• id: C2 claim: Structured logs use key-value pairs. source: S1 evidence: "library. Structured logs use key-value pairs so they can be parsed, filtered,"
• id: C3 claim: Everything becomes a key-value pair in text output. source: S1 evidence: "Everything has been turned into a key-value pair, with strings quoted as needed to preserve"
• id: C4 claim: For more control over output, create a logger with a different handler. source: S2 evidence: "For more control over the output format, create a logger with a different handler."

Sources

• [S1] Structured Logging with slog - The Go Programming Language. The Go Authors (go.dev). https://go.dev/blog/slog . License: CC BY 4.0 (go.dev text). Accessed 2026-11-04.
• [S2] slog package - log/slog - Go Packages. The Go Authors (go.dev). https://pkg.go.dev/log/slog . License: CC BY 4.0 (go.dev text). Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_zjdgwzq3,
  author = {{iinventedlight}},
  title = {{Structured logging with log/slog}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/go-structured-logging-slog/},
  note = {Permanent ID iil:note:zjdgwzq3. License: CC-BY-4.0.},
}

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