c.Infof未定义（类型context.Context没有字段或方法Infof）google.golang.org/appengine/log错误

Question

In the Go Runtime i used the method c.Infof to log messages , but it fails to compile with the following error c.Infof undefined (type context.Context has no field or method Infof) . The Error clearly tells that the app engine context returned from c := appengine.NewContext(r) is of type context.Context and it doesnt have a method c.Infof on it. But contrary to this the documentation in https://godoc.org/google.golang.org/appengine/log suggests that this method exists . Another point to note , The method existed on the context returned by "appengine" (import "appengine" ) package , and this doesnt seem to exist on the context returned by the new package google.golang.org/appengine , what is c.Infof equivalent on the new Context of type context.Context returned by package "google.golang.org/appengine" ?

Answer 1

The example in the package documentation is not correct.

Use the log package functions to write to the App Engine log. Here's the corrected example:

c := appengine.NewContext(r)
query := &log.Query{
    AppLogs:  true,
    Versions: []string{"1"},
}

for results := query.Run(c); ; {
    record, err := results.Next()
    if err == log.Done {
       log.Infof(c, "Done processing results")
       break
    }
    if err != nil {
        log.Errorf(c, "Failed to retrieve next log: %v", err)
        break
    }
    log.Infof(c, "Saw record %v", record)
}

The example in the package documentation was copied from the App Engine Classic package, but not updated to use the new functions. I suggest reporting this to the App Engine Team.