Go coverage with external tests

The Go test coverage implementation is innovative as it allows setting a bit in a coverage bitmap when each code portion is executed. However, there's no straightforward way to obtain coverage data for tests run against the main version of a program. A workaround involves creating a dummy test that executes main(), compiling a binary with go test -c -cover and running only that test instead of the regular binary. This method has been used in RRDNS, a custom Go DNS server. To collect coverage information, run the test battery as usual and use gocovmerge to merge coverage profiles for unit tests.