Hello World using Ciris

Main.scala

package exercise.ciris.qiita1

import ciris.api.Id
import ciris.{ConfigEntry, ConfigErrors, ConfigResult, env, loadConfig, file}
import ciris.generic._

case class Config(name: String)

object Main {
  def main(args: Array[String]): Unit = {
    val entry:  ConfigEntry[Id, String, String, String] = env[String]("NAME")
    val result: ConfigResult[Id, Config] = loadConfig(entry) { name =>
      Config(name)
    }
    val config: Id[Either[ConfigErrors, Config]] = result.result
    val greeting = config.fold(_.message, c => s"Hello, ${c.name}!")
    println(greeting) // "Hello, World!" または "- Missing environment variable [NAME]."
  }
}