Limits Continuity And Differentiability

Let the function $f(x)$ be defined as:
$f(x) = \begin{cases} \left[\tan\left(\dfrac{\pi}{4} + x\right)\right]^{\dfrac{1}{x}}, & x \neq 0 \\ k, & x = 0 \end{cases}$
If $f(x)$ is continuous at $x = 0$, then the value of $k$ is...