Beego當客戶端cookie為空時報錯

2017/11/24 22:24:35 [C] [asm_amd64.s:514] the request url is  /v1/login
2017/11/24 22:24:35 [C] [asm_amd64.s:514] Handler crashed with error runtime error: invalid memory address or nil pointer dereference
2017/11/24 22:24:35 [C] [asm_amd64.s:514] /usr/local/go/src/runtime/asm_amd64.s:514
2017/11/24 22:24:35 [C] [asm_amd64.s:514] /usr/local/go/src/runtime/panic.go:489
2017/11/24 22:24:35 [C] [asm_amd64.s:514] /usr/local/go/src/runtime/panic.go:63
2017/11/24 22:24:35 [C] [asm_amd64.s:514] /usr/local/go/src/runtime/signal_unix.go:290
2017/11/24 22:24:35 [C] [asm_amd64.s:514] /Users/luxingwen/go/src/ynw_wxs/controllers/user.go:51
2017/11/24 22:24:35 [C] [asm_amd64.s:514] /usr/local/go/src/runtime/asm_amd64.s:514
2017/11/24 22:24:35 [C] [asm_amd64.s:514] /usr/local/go/src/reflect/value.go:434
2017/11/24 22:24:35 [C] [asm_amd64.s:514] /usr/local/go/src/reflect/value.go:302
2017/11/24 22:24:35 [C] [asm_amd64.s:514] /Users/luxingwen/go/src/github.com/astaxie/beego/router.go:815
2017/11/24 22:24:35 [C] [asm_amd64.s:514] /usr/local/go/src/net/http/server.go:2568
2017/11/24 22:24:35 [C] [asm_amd64.s:514] /usr/local/go/src/net/http/server.go:1825
2017/11/24 22:24:35 [C] [asm_amd64.s:514] /usr/local/go/src/runtime/asm_amd64.s:2197

具體的 demo 可以看這個哥們的程式碼 https://github.com/it-man-cn/smallapp-session 小程式在沒有登陸之前，客戶端是不會傳 cookie 上來的，所以就報這個錯誤了