How determine the method of moments to this "quasi-Rayleigh" distribution?

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I'm trying to find some estimators to this P.D.F. $$f(x|\theta) = \frac{x}{\theta} exp\left \{ \frac{-x^{2}}{2\theta} \right \}, x \geq 0, \theta\geq 0$$ I already got the MLE! But how can I determine the method of moments, taking in consideration that this P.D.F. is a "quasi-Rayleigh" distribution?