Package env is used to parse environment.
Get returns a value by key. If the key does not exist, the default value will be returned.
GetAll returns all keys/values in the current child process environment.
MustGet returns a value by key. If the key does not exist, it will return an error.
MustSet sets a value in the ENV copy and the child process environment. It returns an error in case the set operation failed.
Set sets a value in the ENV copy. This does not affect the child process environment.