unable to load package '/Users/hammad/.modular/pkg/packages.modular.com_mojo/lib/mojo/stdlib.mojopkg

I just started working on an educational physics engine when suddenly mojo interpreter got angry at me for no reason and started throwing this error:

unable to load package '/Users/hammad/.modular/pkg/packages.modular.com_mojo/lib/mojo/stdlib.mojopkg'mojo

unable to load package '/Users/hammad/.modular/pkg/packages.modular.com_mojo/lib/mojo/stdlib.mojopkg'mojo

unable to load package '/Users/hammad/.modular/pkg/packages.modular.com_mojo/lib/mojo/stdlib.mojopkg'mojo

unable to load package '/Users/hammad/.modular/pkg/packages.modular.com_mojo/lib/mojo/stdlib.mojopkg'mojo

Code:

struct System:
    elasticPotentialEnergy = 0.0
    kineticEnergy = 0.0
    gravitaionalPotentialEnergy = 0.0
    ...

struct System:
    elasticPotentialEnergy = 0.0
    kineticEnergy = 0.0
    gravitaionalPotentialEnergy = 0.0
    ...

struct System:
    elasticPotentialEnergy = 0.0
    kineticEnergy = 0.0
    gravitaionalPotentialEnergy = 0.0
    ...

struct System:
    elasticPotentialEnergy = 0.0
    kineticEnergy = 0.0
    gravitaionalPotentialEnergy = 0.0
    ...

What's wrong?