Fix loading large integers from JSON files

[severb]

%v uses E notation to format floats with more than 6 digits. Since JSON numbers are always floats, Kong breaks when loading large integers from JSON files.

[alecthomas]

Nice find, thanks!

[purplefox]

I suspect this will still fail with very large integers, e.g. max Int64: 9223372036854775807 if it's marshalling into a float64, as it's not possible to represent this number exactly as a float64.

I came across a similar problem in Prana when unmarshalling JSON Kafka messages which have large numbers in their fields. The solution in Prana was not to use the default Go Json unmarshalling (which treats all numbers as float64), but to unmarshall into a map, preserving the original form, then doing a strconv.parseInt(...) on the field to convert it into a int64 without losing precision.

[purplefox]

Hey @alecthomas - any thoughts on the above?

[alecthomas]

If the target field is a float64 then that would be expected wouldn't it? If you want to support very large integers try int64, big.Int, or big.Float, do those work?