spec/common_specs/all: fix typo
spec/src/web_server: add more debugging information
Do not "bundle exec" in the Go context
WebServer: shutdown in a more robust way

This way isn't the most robust, though. I had to build the go executable
manually, because if I run the Nethttp example with "go run main.go", it
creates two identical "main" processes. So in total I have 3 processes
to kill. But it's a rabbit hole trying to find the third process. It's
easier to build manually.