example koa based proxy

example-api.js

// imagine that this is the api you want your proxy to interface with
const Koa = require('koa')
const app = new Koa()

app.use(async ctx => {
    console.log(ctx.request.method + ' ' + ctx.request.url)
    console.log(ctx.request.header['content-type'])
    ctx.set('content-type', 'whatevs')
    ctx.body = 'yolo'
})

app.listen(3001)

proxy.js

// this is the thing that your services would actually use
const got = require('got')
const Koa = require('koa')
const app = new Koa()

const baseUrl = 'http://localhost:3001'

// you'd probably want some sort of authentication for your services
app.use(async ctx => {
    console.log(ctx.request.method + ' ' + ctx.request.url)
    const incomingContentType = ctx.request.header['content-type']
    const headers = incomingContentType
        ? { 'content-type': incomingContentType }
        : undefined

    // in here somewhere is where you'd manage authenticating to the external api

    // pass the url and optional headers through
    const stream = got.stream(baseUrl + ctx.request.url, { headers })
    stream.on('response', response => {
        // whatever headers come back from the api you can pass along
        const contentType = response.headers['content-type']
        ctx.set('content-type', contentType)
    })
    ctx.body = stream
})

app.listen(3000)