A dependency-free TOML 1.0 parser for Go — standard library only, no third-party modules. Passes the entire toml-test suite (185 valid and 371 invalid cases).

interpres (Latin for interpreter) reads TOML documents into Go values with a small, encoding/json-style API. It is built for embedding in zero-dependency Go programs that still want their configuration in TOML.

Install

go get codeberg.org/petrbalvin/interpres

Requires Go 1.26 or newer. The module imports only the standard library.

Usage

Decode into a struct

package main

import (
	"fmt"

	"codeberg.org/petrbalvin/interpres"
)

type Config struct {
	Title  string `toml:"title"`
	Server struct {
		Host string `toml:"host"`
		Port int    `toml:"port"`
	} `toml:"server"`
}

func main() {
	data := []byte(`
title = "example"

[server]
host = "127.0.0.1"
port = 9090
`)

	var cfg Config
	if err := interpres.Unmarshal(data, &cfg); err != nil {
		panic(err)
	}
	fmt.Printf("%+v\n", cfg)
}

Untyped tree

tree, err := interpres.Parse(data) // map[string]any

Strict decoding

Reject keys that have no matching struct field — useful for catching typos in configuration files:

err := interpres.NewDecoder().
	DisallowUnknownFields().
	Decode(data, &cfg)

Struct mapping

Fields are matched to TOML keys by the toml:"name" tag, or by a case-insensitive match on the field name when no tag is present. A tag of "-" skips the field.

TOML value	Go type (untyped tree)
string	`string`
integer	`int64`
float	`float64`
boolean	`bool`
offset date-time	`time.Time`
local date-time	`LocalDateTime`
local date	`LocalDate`
local time	`LocalTime`
array	`[]any`
table / inline table	`map[string]any`
array of tables	`[]map[string]any`

When decoding into a struct, these map onto the destination's concrete types (any integer/unsigned/float width, slices, nested structs, and map[string]T).

TOML 1.0 support

interpres implements the full TOML 1.0 grammar:

Comments, and bare / quoted / dotted keys.
Tables [a.b] and arrays of tables [[a]].
Basic and literal strings, including multiline (""" / ''') with escape sequences (\n, \t, \uXXXX, \UXXXXXXXX, line-ending backslash).
Integers in decimal, hex (0x), octal (0o), and binary (0b) with _ separators; floats with exponents and inf / nan.
Booleans, offset/local date-times, dates, and times.
Arrays (multiline, mixed types) and inline tables.

Invalid documents are rejected per the specification (malformed numbers and floats, control characters, non-UTF-8 input, out-of-range escapes, table and inline-table redefinitions, and more).

Compliance

The parser is verified against the official toml-test suite via cmd/interpres-decode:

go build -o interpres-decode ./cmd/interpres-decode
toml-test ./interpres-decode

README.md

interpres