code: function getVariable(configName, variableName) {
      return new Promise(function(resolve, reject) {
          auth().then(function(authClient) {
              const projectId = process.env.GCLOUD_PROJECT;
              const fullyQualifiedName = 'projects/' + projectId
                      + '/configs/' + configName
                      + '/variables/' + variableName;
  
              runtimeConfig.projects.configs.variables.get({
                  auth: authClient,
                  name: fullyQualifiedName,
              }, function(err, res) {
                  if (err) {
                      reject(err);
                      return;
                  }
  
                  const variable = res.data;
                  if (typeof variable.text !== 'undefined') {
                      resolve(variable.text);
                  } else if (typeof variable.value !== 'undefined') {
                      resolve(Buffer.from(variable.value, 'base64').toString());
                  } else {
                      reject(new Error('Property text or value not defined'));
                  }
              });
          });
      });
  }
docs: runtimeConfig.getVariable
  
  @desc Reads a runtime config value
  
  @param {string} configName The config name of the variable to return
  @param {string} variableName The variable name of the variable to return
  @return {Promise} Promise that resolves the variable value