英文:
Runtime panic when using http.Server under GAE
问题
我的代码在这里：
http://play.golang.org/p/RehA28iJtA
为什么当我在浏览器中输入"http://example.com:8080/download"时会显示以下错误？
错误信息：
运行时进程返回了错误的HTTP响应：''
2014/05/14 13:07:50 http: panic serving 127.0.0.1:59525: 运行时错误：无效的内存地址或空指针解引用
goroutine 3 [running]:
net/http.func·009()
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1093 +0xae
runtime.panic(0x646520, 0x94ba48)
/tmp/appengine/go_appengine/goroot/src/pkg/runtime/panic.c:248 +0x106
xflight.Download(0x7fcade6926b8, 0xc21000f6e0, 0xc21005ea90)
xflight/xflight.go:21 +0x132
net/http.HandlerFunc.ServeHTTP(0x71b6e8, 0x7fcade6926b8, 0xc21000f6e0, 0xc21005ea90)
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1220 +0x40
net/http.(*ServeMux).ServeHTTP(0xc21001e630, 0x7fcade6926b8, 0xc21000f6e0, 0xc21005ea90)
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1496 +0x163
appengine_internal.handleFilteredHTTP(0x7fcade6926b8, 0xc21000f6e0, 0xc21005ea90)
/tmp/appengine/go_appengine/goroot/src/pkg/appengine_internal/api_dev.go:98 +0x2e2
net/http.HandlerFunc.ServeHTTP(0x6fe040, 0x7fcade6926b8, 0xc21000f6e0, 0xc21005ea90)
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1220 +0x40
net/http.serverHandler.ServeHTTP(0xc21000b640, 0x7fcade6926b8, 0xc21000f6e0, 0xc21005ea90)
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1597 +0x16e
net/http.(*conn).serve(0xc210058380)
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1167 +0x7b7
created by net/http.(*Server).Serve
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1644 +0x28b
英文:
My code is here:
http://play.golang.org/p/RehA28iJtA
Why when I enter "http://example.com:8080/download" to the browser it shows a following error?
Error:
the runtime process gave a bad HTTP response: ''
2014/05/14 13:07:50 http: panic serving 127.0.0.1:59525: runtime error: invalid memory address or nil pointer dereference
goroutine 3 [running]:
net/http.func·009()
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1093 +0xae
runtime.panic(0x646520, 0x94ba48)
/tmp/appengine/go_appengine/goroot/src/pkg/runtime/panic.c:248 +0x106
xflight.Download(0x7fcade6926b8, 0xc21000f6e0, 0xc21005ea90)
xflight/xflight.go:21 +0x132
net/http.HandlerFunc.ServeHTTP(0x71b6e8, 0x7fcade6926b8, 0xc21000f6e0, 0xc21005ea90)
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1220 +0x40
net/http.(*ServeMux).ServeHTTP(0xc21001e630, 0x7fcade6926b8, 0xc21000f6e0, 0xc21005ea90)
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1496 +0x163
appengine_internal.handleFilteredHTTP(0x7fcade6926b8, 0xc21000f6e0, 0xc21005ea90)
/tmp/appengine/go_appengine/goroot/src/pkg/appengine_internal/api_dev.go:98 +0x2e2
net/http.HandlerFunc.ServeHTTP(0x6fe040, 0x7fcade6926b8, 0xc21000f6e0, 0xc21005ea90)
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1220 +0x40
net/http.serverHandler.ServeHTTP(0xc21000b640, 0x7fcade6926b8, 0xc21000f6e0, 0xc21005ea90)
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1597 +0x16e
net/http.(*conn).serve(0xc210058380)
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1167 +0x7b7
created by net/http.(*Server).Serve
/tmp/appengine/go_appengine/goroot/src/pkg/net/http/server.go:1644 +0x28b
答案1
得分: 4
你不能在App Engine中使用默认的HTTP客户端。你需要在这里使用URL Fetch服务 https://developers.google.com/appengine/docs/go/urlfetch/
示例：http://play.golang.org/p/Gf-WzLmP09
英文:
You cannot use default http client in App Engine. You need to use URL Fetch service here https://developers.google.com/appengine/docs/go/urlfetch/
Example: http://play.golang.org/p/Gf-WzLmP09
答案2
得分: 0
在你的示例中，func main() 缺失。
顺便说一下，在 func Download() 中，你使用的是 string 而不是 variable，如果你访问 http://127.0.0.1:8080/download，你总是会得到 "resp"。
英文:
In your example func main() is missing.
Btw, in func Download() - you use string not variable, and if you go to http://127.0.0.1:8080/download - you always will get "resp".
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