Tag reference

Attach Fuda tags to exported struct fields.

Tag	Example	Purpose
yaml	yaml:"host"	Maps a YAML key to the field.
json	json:"host"	Maps a JSON key to the field.
default	default:"8080"	Supplies a value when no source supplied one.
env	env:"APP_PORT"	Reads an environment override.
ref	ref:"file:///run/secrets/token"	Resolves a fixed external URI.
refFrom	refFrom:"TokenURI"	Resolves the URI stored in an earlier field.
dsn	dsn:"postgres://${.Host}:5432/app"	Builds a string from fields, env values, or references.
dsnStrict	dsnStrict:"true"	Makes a DSN fail when an expression is empty.
validate	validate:"required"	Applies a validator rule after loading.

Tags can work together:

type Config struct {
    Host string `yaml:"host" default:"localhost" env:"APP_HOST"`
    Port int    `yaml:"port" default:"8080" env:"APP_PORT" validate:"min=1,max=65535"`
}

For the basic value rule, read Choose a value. For external values, read Load external references.