code: public static String replaceEnv(String configString) {
          Properties properties = new Properties();
          
          for (Map.Entry<String, String> entry : System.getenv().entrySet()) {
              properties.put("env." + entry.getKey(), entry.getValue());
          }
          String replaced = StringPropertyReplacer.replaceProperties(configString, properties);
          //remove env placeholders that were not replaced with values
          return replaced.replaceAll("\\$\\{env\\..+\\}", "");
      }
docs: Replace environment variables in string.
  Environment variables are expected in format ${env.ENV_PROPERTY},
  where "env" is static prefix and ENV_PROPERTY is name of environment property.
  
  @param configString String with environment variables
  @return String with replaced environment variables