The original issue was caused by the fact that if we use a very large
unix timestamp. The resulting value from time.UnixNano overflows a
int64, as documented here: https://pkg.go.dev/time#Time.UnixNano.

This patch works around the issue by calculating the second part and
nanosecond part separately, taking the second part from time.Unix,
and the nanosecond part from time.Nanosecond and then adding the
results together.

We now format the whole part and the decimal part separately.

Since the whole part is by definition, we need not covert it to a float,
hence the whole part can simply be formatted as an integer.

The and since by definition of the `Time.Nanoseconds()`, the return
value is between 0-999999999, only this part needs to be formatted
separately.

We then combine whole + decimals[1:] to form the final result.

This allows us to correctly format the maximun timestamp that is allowed
by Go.

used to marshal times.

Improved variable naming and fixed typos.

…flow