AWS SNS网络服务订阅——快件，辛纳屈的例子

I'm simply trying to build an auto-subscription API which POSTs back the token. I can do this very easily in Sinatra (render the POSTed JSON from AWS) -- seem to be having a hard time in Express; I'm sure it's just something stupid I'm missing, though I've tried 1000X combinations.I'm simply trying to build an auto-subscription