feat: support SCF apigateway event structure

Juliiii commented 4 years ago

Hello, here is why i make this pr.

I try to use koa in TencentCloud Serverless Cloud Functions with serverless-http. Everything seems ok. But i found a case that if i create a apigateway trigger in their console, they will not configure query params in the TencentCloud Apigateway. So when i create a function which returns ctx.query, and request the apigateway path like curl https://service-818xjkw2-1252618971.gz.apigw.tencentcs.com/release/blog_visit?a=1&b=2

i can not get the query params in queryStringParameters, but in queryString and the docs of them also says this case. Link