Compose a DSN

Use dsn to build a connection string after Fuda has processed ordinary fields, environment values, references, and defaults.

type Config struct {
    Host     string `yaml:"host" default:"localhost"`
    Port     int    `yaml:"port" default:"5432"`
    User     string `env:"DB_USER"`
    Password string `ref:"env://DB_PASSWORD"`
    DSN      string `dsn:"postgres://${.User}:${.Password}@${.Host}:${.Port}/app" dsnStrict:"true"`
}

Keep Host, Port, User, and Password before DSN in the struct. Fuda then has their final values when it expands ${.Field} expressions.

Use URI templates

Use an environment value or reference inside a DSN template when it does not need its own struct field:

RedisDSN string `dsn:"redis://:${env:REDIS_PASSWORD}@${.Host}:6379/0"`

MongoDSN string `dsn:"mongodb://admin:${ref:file:///run/secrets/mongo_password}@${.Host}:27017/app"`

Use WithTimeout when an inline reference reaches an HTTP endpoint.

Fail on missing fields

By default, a missing DSN expression becomes an empty string. Add dsnStrict:"true" to return an error instead. This protects connection strings that require every field.

Next step

Render a configuration template before Fuda decodes it.