Content length response header incorrectly parsed

[kerim1]

When requesting the length using ctx.length, Koa parses the content length response header using the double tilde operator: https://github.com/koajs/koa/blob/master/lib/response.js#L214 However, this operation also performs a 32-bit conversion, resulting in incorrect and weird results when serving large files. Isn't it therefore better to use the Math.trunc() function instead to parse the content length response header?

[fl0w]

Or BigInt for node >=10.4.

[tpscrpt]

using Math.trunc is 5% slower on 100 000 000 iterations of res.length when it's set to 164 chars.

[fl0w]

Fixed in 9be858312553002841725b617050aaff3c48951d