I would like to recommend an excellent Mac application: Loopback from Rogue Amoeba. It allows you to select applications to reroute their audio output and use as input for another application. In this situation, I route Google Chrome to create a "Chrome output" sound source. I then configure GoToMeeting to use "Chrome Output" as the microphone. To keep myself in the sound, I also configure the "Chrome output" to include my Yeti Microphone as an input after filtering through Audio Hijack. Here is a snapshot of my Loopback configuration:
It is reasonably priced and paired with Audio Hijack it can even filter your audio (get rid of background noises). They also have several other powerful applications that are all very well made and reasonably priced.