rsnext/examples/environment-variables/environment.d.ts

declare namespace NodeJS {
  export interface ProcessEnv {
    readonly ENV_VARIABLE: string;
    readonly NEXT_PUBLIC_ENV_VARIABLE: string;

    readonly DEVELOPMENT_ENV_VARIABLE: string;
    readonly NEXT_PUBLIC_DEVELOPMENT_ENV_VARIABLE: string;

    readonly ENV_LOCAL_VARIABLE: string;
    readonly NEXT_PUBLIC_ENV_LOCAL_VARIABLE: string;

    readonly PRODUCTION_ENV_VARIABLE: string;
    readonly NEXT_PUBLIC_PRODUCTION_ENV_VARIABLE: string;
  }
}