①: Error: Can't set headers after they are sent.
at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:356:11)
at ServerResponse.header (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/express/lib/response.js:719:10)
at ServerResponse.send (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/express/lib/response.js:164:12)
at done (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/express/lib/response.js:956:10)
at tryHandleCache (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/ejs/lib/ejs.js:208:10)
at View.exports.renderFile [as engine] (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/ejs/lib/ejs.js:412:10)
at View.render (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/express/lib/view.js:126:8)
at tryRender (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/express/lib/application.js:639:10)
at EventEmitter.render (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/express/lib/application.js:591:3)
at ServerResponse.render (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/express/lib/response.js:960:7)
/Users/hmc/Desktop/SongsService/ReadingService/node_modules/mysql/lib/protocol/Parser.js:79
throw err; // Rethrow non-MySQL errors
^
解决办法:return 太多

②: TypeError: req.next is not a function
at done (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/express/lib/response.js:955:25)
at tryRender (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/express/lib/application.js:641:5)
at EventEmitter.render (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/express/lib/application.js:591:3)
at ServerResponse.render (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/express/lib/response.js:960:7)
at /Users/hmc/Desktop/SongsService/ReadingService/routes/index.js:73:25
at Query._callback (/Users/hmc/Desktop/SongsService/ReadingService/db/DBDao.js:217:21)
at Query.Sequence.end (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/mysql/lib/protocol/sequences/Sequence.js:86:24)
at Query._handleFinalResultPacket (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/mysql/lib/protocol/sequences/Query.js:137:8)
at Query.EofPacket (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/mysql/lib/protocol/sequences/Query.js:121:8)
at Protocol._parsePacket (/Users/hmc/Desktop/SongsService/ReadingService/node_modules/mysql/lib/protocol/Protocol.js:280:23)

Process finished with exit code 1

解决办法: 数据库没有完成就进行了 release()操作