gitagal said:
I am sure I planted it for the flowers and the butterflies and bees to feast on.
Di NOT expect it to be so lanky 
Gita
If it gets too tall, you can always cut if off to the ground. It will grow back just fine, but be somewhat shorter. The more times you cut it back, the shorter and bushier it will be.
That being said, many species of goldenrod make excellent garden plants but Canada Goldenrod isn't one of them (in my opinion of course). It can be an aggressive spreader, especially if you intend to confine it to a small space.
