为什么在此代码的函数结尾处缺少返回值？

之所以会出现此错误，是因为

else

}

func getKeyNameFromDeploymentAndSubnet(subnetType SubnetType, deploymentType DeploymentType, keyNameMap map[SubnetType]string) string {    if deploymentType == NoDeployment || deploymentType == PDBAWindows || deploymentType == AgentDeployment {        return keyNameMap[subnetType]    } else if deploymentType == AnsibleDeployment {        return "bar"    }    return "foo"}