For the electromagnetic lagrangian $L = 1/2mu^2 - q(\phi - \frac{\vec A}{c}\cdot \vec u)$, what gauge is used for A?

For the Lagrangian $$L = \frac{1}{2}mu^2 - q(\phi - \frac{\vec{A}}{c}\cdot \vec{u})$$ of a non-relativistic point particle in an electromagnetic potential, what gauge is used for the electromagnetic potential $\vec{A}$ and $\phi$?