CLI Reference

The constago command loads configuration, scans Go source files, and writes one generated file in every package containing selected structs.

constago [flags]

Configuration lookup

With no --config flag, Constago looks for constago.yaml in the current working directory. A missing default file is allowed; explicit flags and built-in defaults are still applied.

Use a specific file with:

constago --config ./config/constago.yaml

Only changed flags override YAML values. Because elements and getters are nested collections, define them in YAML.

Environment overrides

Environment variables use the CONSTAGO_ prefix and replace dots in configuration keys with underscores. For example:

CONSTAGO_VERBOSE=2 \
CONSTAGO_OUTPUT_FILE_NAME=fields.gen.go \
constago --config constago.yaml

Environment overrides are most reliable for keys already represented in the YAML file. Use YAML for elements and getters, and use flags when you need a guaranteed one-off override.

Flags

Flag	Value	Purpose
--config	path	YAML configuration file
--verbose	0, 1, or 2	Silent, steps, or steps plus element details
--input.dir	path	Root directory to scan
--input.include	string list	Include Go globs or package:NAME selectors
--input.exclude	string list	Exclude Go globs or package:NAME selectors
--input.struct.explicit	boolean	Require //constago:include on structs
--input.struct.include_unexported	boolean	Include unexported structs
--input.struct.only	regex	Include only matching struct names
--input.struct.except	regex	Exclude matching struct names
--input.field.explicit	boolean	Require a constago tag on fields
--input.field.include_unexported	boolean	Include unexported fields
--input.field.only	regex	Include only matching field names
--input.field.except	regex	Exclude matching field names
--output.file_name	filename	Generated Go filename, without directories

Pass multiple include or exclude values as a comma-separated list:

constago \
  --input.dir . \
  --input.include '**/*.go,package:model' \
  --input.exclude '**/*_test.go,package:fixtures' \
  --output.file_name fields.gen.go

Quote glob patterns so your shell does not expand them before Constago receives them.

Verbosity

• 0 produces no progress output.
• 1 reports scanning and generation steps. This is the default.
• 2 also reports selected generated elements.

Exit behavior

Configuration, scanning, or generation failures cause the command to return an error. The current executable reports that error as a panic, so CI should rely on the non-zero exit status rather than parse its text.

Inspect help

The installed binary is the source of truth for flags:

constago --help