Profiling Go allocations typically makes leaks clear. http://blog.golang.org/2011/06/profiling-go-programs.html

If you are worried about leaking goroutines,

  import _ "net/http/pprof"

in your web server and then visit /debug/pprof/goroutine (or even just /debug/pprof). That listing shows all the active goroutine stacks, but it groups bunches with the same stack into a single entry with a count. Scanning the list it is usually easy to see leaks (hey, why do I have 5000 goroutines with that stack) and also why they are stuck (because you have the whole stack).