When js file doesn't exist, chrome sometimes makes two requests

[vladshcherbin]

Hey,

I'm was trying a basic koa server setup and saw an interesting thing - if I request a js file which doesn't exist, chrome makes two requests sometimes for it which can be seen on network a panel. Chrome doesn't always make two requests, only sometimes (like 50% or smth).

I found out this using koa-static, but it also happens with bare koa-send as it's used inside of koa-static.

Any idea why this can be happening? I can make a demo repo if needed.