Google App Engine goapp可以“部署”，但是“服务”失败，这是怎么回事？

Question

I started using Google App Engine today, so hopefully the answer will be obvious to someone with experience. After simply following this method to get App Engine interfacing with Cloud SQL, I'm having a frustrating issue: goapp deploy succeeds but goapp serve fails (using the cloud shell).

Here's the error:

XXXX@cloudshell:~/src/XXXX/app-engine (XXXX)$ goapp serve app.yaml
INFO     2018-06-21 07:29:08,115 devappserver2.py:764] Skipping SDK update check.
INFO     2018-06-21 07:29:08,235 api_server.py:268] Starting API server at: http://0.0.0.0:60628
INFO     2018-06-21 07:29:08,305 dispatcher.py:199] Starting module "default" running at: http://0.0.0.0:8080
INFO     2018-06-21 07:29:08,306 admin_server.py:116] Starting admin server at: http://0.0.0.0:8000
ERROR    2018-06-21 07:29:12,254 go_runtime.py:181] Failed to build Go application: (Executed command: /google/go_appengine/goroot/bin/go-app-builder -app_base /home/XXX/app-engine -arch 6 -dynamic -goroot /google/go_appengine/goroot -gopath /home/XXX/gopath:/google/gopath -nobuild_files ^^$ -incremental_re
build -unsafe -binary_name _go_app -extra_imports appengine_internal/init -work_dir /tmp/tmpT1RTRMappengine-go-bin -gcflags -I,/google/go_appengine/goroot/pkg/linux_amd64_appengine -l
dflags -L,/google/go_appengine/goroot/pkg/linux_amd64_appengine hello.go)
/home/XXX/gopath/src/github.com/go-sql-driver/mysql/connection.go:12: can't find import: "context"
2018/06/21 07:29:09 Can't find package "context" in $GOPATH: cannot find package "context" in any of:
    /google/go_appengine/goroot/src/context (from $GOROOT)
    /home/XXX/gopath/src/context (from $GOPATH)
    /google/gopath/src/context
2018/06/21 07:29:12 go-app-builder: build timing: 0×skip (3ms total), 9×compile (2.731s total), 0×link (0 total)
2018/06/21 07:29:12 go-app-builder: failed running compile: exit status 2

I'm suspicious that the version of go being used is wrong. The stated version is 1.6.3 but as I understand "context" requires 1.7. Here's the relevant cloud shell output for that:

XXXX@cloudshell:~ (XXX)$ goapp version
go version go1.6.3 (appengine-1.9.48) linux/amd64
XXXX@cloudshell:~ (XXX)$ go version
go version go1.10 linux/amd64

However, despite my best efforts I have been unable to find any resources on how to manipulate the "goapp" go version.

My app.yaml includes:

runtime: go
api_version: go1.8

And goapp get yields this:

XXXX@cloudshell:~/src/XXX/app-engine (XXX)$ goapp get
package context: unrecognized import path "context" (import path does not begin with hostname)

The go file itself is an exact copy of the demo from the linked above.

Answer 1

In Google App Engine, if you need to get a context, you should probably use google.golang.org/appengine.NewContext() for a context during an HTTP request, or google.golang.org/appengine.BackgroundContext() if it's outside a request. Both return context.Context, which is the same that you would get by creating a context through the context package, but with a context prepared to be used within GAE.

This does not tell you why the imports are not working (other than goapp looks to be using 1.6), but will just work around the issue avoiding you to import any context package.