Allow for response time logging in access logs

[KaranTrivedi]

Checklist

• There are no similar issues or pull requests for this yet.
• I discussed this idea on the community chat and feedback is positive.

Is your feature related to a problem? Please describe.

I am able to log user requests in the access logs, but not able to track response times.

Describe the solution you would like.

I hope the access logs allows for a pattern that lets user to define pattern in logger to capture response time

Current:

"access": {
            "()": "uvicorn.logging.AccessFormatter",
            "datefmt": "%Y-%m-%dT%H:%M:%S%z",
            "fmt": '%(asctime)s::%(levelprefix)s %(client_addr)s - "%(request_line)s" %(status_code)s',
            "use_colors": False,
        },

Future:

"access": {
            "()": "uvicorn.logging.AccessFormatter",
            "datefmt": "%Y-%m-%dT%H:%M:%S%z",
            "fmt": '%(asctime)s::%(levelprefix)s %(client_addr)s - "%(request_line)s" **%(resp_time)s** %(status_code)s',
            "use_colors": False,
        },

Describe alternatives you considered

I was suggested third party tool in the community chat:
https://github.com/steinnes/timing-asgi

Seems like an improper solution for this. The response time is not embedded in the access log itself...

Sample log from library git page..

INFO: Started server process [35895]
INFO: Waiting for application startup.
2019-03-07 11:38:01 INFO  [timing_asgi.middleware:44] ASGI scope of type lifespan is not supported yet
INFO: Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO: ('127.0.0.1', 58668) - "GET / HTTP/1.1" 200
myapp.__main__.homepage 0.0006690025329589844 ['http_status:200', 'http_method:GET', 'time:wall']
myapp.__main__.homepage 0.0006950000000000012 ['http_status:200', 'http_method:GET', 'time:cpu']
INFO: ('127.0.0.1', 58684) - "GET /asdf HTTP/1.1" 404
myapp.asdf 0.0005478858947753906 ['http_status:404', 'http_method:GET', 'time:wall']
myapp.asdf 0.0005909999999999804 ['http_status:404', 'http_method:GET', 'time:cpu']

Additional context

No response

[Kludex]

Duplicated #527