我不断遇到这些无法处理的承诺被拒绝的错误，在运行测试期间将它们发送到客户端后无法设置标头。有人可以解释我所缺少的吗？
(node:4929) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
at ServerResponse.setHeader (_http_outgoing.js:482:11)
at ServerResponse.header