英文:
cannot find package "appengine/cloudsql"
问题
我使用Google Cloud SQL和MySQL服务器开发了一些GO库。当我导入appengine/cloudsql时，出现了以下错误。
cloud.go:20:2: 在以下任何位置都找不到包“appengine/cloudsql”：
/usr/local/Cellar/go/1.1.2/src/pkg/appengine/cloudsql（来自$GOROOT）
/Users/lameduck/myGo/src/appengine/cloudsql（来自$GOPATH）
我知道这个包appengine/cloudsql只适用于Google App Engine，而且在其他地方是不存在的。
我想知道如何在单个库中同时为GAE和其他环境使用它和标准的SQL库。
PS：我可以正确设置Google App Engine SDK。我的问题与此无关。我希望我的库能在Google App Engine和独立环境中同时运行（我已经为GAE编写了一段代码，为其他数据库编写了另一段代码）。用户需要设置一些配置是可以的，但我不希望用户修改库源代码。
感谢任何帮助。
英文:
I develop some GO libraries using Google Cloud SQL and MySQL server. When I imported `appengine/cloudsql, an error below occured.
cloud.go:20:2: cannot find package "appengine/cloudsql" in any of:
/usr/local/Cellar/go/1.1.2/src/pkg/appengine/cloudsql (from $GOROOT)
/Users/lameduck/myGo/src/appengine/cloudsql (from $GOPATH)
I know this package, appengine/cloudsql, is only for Google App Engine and it doesn't exist on everywhere else.
I'm wondering how can I use it for GAE and standard sql library for other environments in a single library.
PS: I can setup Google App Engine SDK correctly. My question is not relevant to it. I hope my library runs on Google App Engine and standalone environment together. (I already made a code for GAE and a code for other dabatases.) It is Ok that users have to setup some configurations. But I don't want that users have to modify a library source code.
Thanks for any help.
答案1
得分: 3
我解决了这个问题。我使用了一个构建约束来使用适当的例程并避免错误。对于App Engine，有一个构建约束叫做appengine。
> App Engine SDK引入了一个新的构建约束术语："appengine"。指定了
> // +build appengine 的文件将由App Engine SDK构建，并被go工具忽略。相反，指定了
> // +build !appengine 的文件将被App Engine SDK忽略，而go工具将愉快地构建它们。
PS：无论如何，我给其他答案点了赞。谢谢。
英文:
I solved the problem. I used a build constraint to use the proper routine and avoid an error. There is a build constraint for App Engine, appengine.
> The App Engine SDK introduces a new build constraint term:
> "appengine". Files that specify
>
> // +build appengine will be built by the App Engine SDK and ignored by
> the go tool. Conversely, files that specify
>
> // +build !appengine are ignored by the App Engine SDK, while the go
> tool will happily build them.
PS:
Anway, I upvoted other answers. Thank you.
答案2
得分: 1
包的导入是在编译/链接时完成的。与Python不同，Go不支持运行时条件导入。
你要寻找的功能是动态库加载（就像在C/C++中可以在运行时加载.so/.dll文件），但是目前Go不支持这个功能。你可以参考这个链接。
英文:
Package import is done during compile/link time. And Go doesn't support runtime conditional imports in distinction from Python.
Feature you are looking for is dynamic library loading (like in C/C++ you can load .so/.dll in runtime), but Go currently doesn't support it.
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