First-order equation $y'+2y=e^{-t}\theta(t)$ with Heaviside forcing

Solve \(y ^ { \prime } + 2 y = e ^ { - t } \theta ( t )\) , where θ is the Heaviside function, \(\theta ( x ) = 0 { \mathrm { ~ i f ~ } } x < 0\) and \(\theta ( x ) = 1 { \mathrm { ~ i f ~ } } x > 0\)