x/website: os.WriteFile example fails to run

[lekan-pvp]

What version of Go are you using (go version)?

$ go version
1.16

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

Ubuntu 20.04 amd64

go env Output

$ go env

What did you do?

run example on site under func os.WriteFile

https://play.golang.org/p/mCCjFLaE9Ua

What did you expect to see?

nothing

What did you see instead?

2009/11/10 23:00:00 open testdata/hello: no such file or directory

[cherrymui]

Thanks for reporting. See #9679. Closing as a dup..