Root path is applied 2 times when using root_path

[Mindaugas Jaraminas]

Here is error:

Python 3.7.8
fastapi 0.63.0

Run configuration:
uvicorn.run("app:app", host="0.0.0.0", port=port, reload=True)

I think the error is in the path here is console log:
127.0.0.1:54913 - "GET /api/v1/api/v1/openapi.json HTTP/1.1" 404 Not Found
Here is double path: /api/v1/api/v1/

Doc path is wrong http://localhost:8080/docs I expect it to be: http://localhost:8080/api/v1/docs

Here is the test code to reproduce 'test_app.py' file:

import uvicorn
import json
from fastapi import FastAPI, APIRouter, Response
from fastapi.responses import RedirectResponse

app = FastAPI(title="Root path test", root_path="/api/v1")

@app.post("/test-call ", tags=["test"])
def ping():
    return Response(
        json.dumps(dict(ping='pong')), 
        headers={'Content-Type':'application/json'})

@app.get("/")
def read_typer():
    return RedirectResponse('/docs')


if __name__ == "__main__":
    uvicorn.run("test_app:app", host="0.0.0.0", port=8080, reload=True)

[Sebastián Ramírez]

root_path is to be used behind a proxy, check the docs here, including how to test that with Traefik: https://fastapi.tiangolo.com/advanced/behind-a-proxy/

Sorry for the long delay! 🙈 I wanted to personally address each issue/PR and they piled up through time, but now I'm checking each one in order.

[github-actions]

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