Of course you will ... think of it, the flash is being blocked by a lens that is taking a 180° photo of what is in front of the camera.
The widest flashes only cover 84° so even if the lens was not in the way of the flash, you would get some amazing vignetting.
For no shadow you have two options.
1) use a couple of external flash units on either side of your camera or
2) steady the camera on a tripod or something and do not use the flash, just the light that is present.