https://blog.golang.org/context uses the following code to cancel the
request if ctx.Done is closed before the goroutine exits:
func httpDo(ctx context.Context, req *http.Request, f func(*http.Response,
error) error) error {
// Run the HTTP request in a goroutine and pass the response to f.
c := make(chan error, 1)
req = req.WithContext(ctx)
go func() { c <- f(http.DefaultClient.Do(req)) }()
select {
case <-ctx.Done():
<-c // Wait for f to return.
return ctx.Err()
case err := <-c:
return err
}
}
I have two questions about this piece of code.
First, if neither "http.DefaultClient.Do" nor "f" does a check of
"ctx.Done()", "f(http.DefaultClient.Do(req))" can't be cancelled. It means
that if I want to use "ctx.Done()" to cancel some functions, I need to
check "ctx.Done()" at various points in the functions which I want to
cancel. Is my understanding correct?
Second, if I don't want to do a cleanup of "http.DefaultClient.Do" and "f",
I can just remove "<-c // Wait for f to return.". If I do this, there will
be a dangling running goroutine after httpDo returns. Is this approached
considered bad?
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