request.get does not return


When using `request.get("https://google.com/"),` i dont receive any response.

When i add a request.get("https://google.com/", timeout=5) i receive the response after 5 seconds! >> 0:00:05.223328.
if i switch the timeout to 10, it takes 10 second and etc...

if I request a simple html file, this problem doesnt occur.

 request.get("http://www.brainjar.com/java/host/test.html", timeout=5") >> 0:00:00.212320.


## Reproduction Steps

```python
import requests

r = requests.get('http://www.google.com', timeout=5)

[print(key, value) for key, value in r.__dict__.items() if key!='_content']

b = requests.get("http://www.brainjar.com/java/host/test.html", timeout=5)

print("\n\n\nSecond Request", b.elapsed)
```
What i Get:
```
_content_consumed True
_next None
status_code 200
headers {'Date': 'Mon, 29 Jun 2020 21:20:13 GMT', 'Expires': '-1', 'Cache-Control': 'private, max-age=0', 'Content-Type': 'text/html; charset=ISO-8859-1', 'P3P': 'CP="This is not a P3P policy! See g.co/p3phelp for more info."', 'Content-Encoding': 'gzip', 'Server': 'gws', 'Content-Length': '5373', 'X-XSS-Protection': '0', 'X-Frame-Options': 'SAMEORIGIN', 'Set-Cookie': '1P_JAR=2020-06-29-21; expires=Wed, 29-Jul-2020 21:20:13 GMT; path=/; domain=.google.com; Secure, NID=204=jAqS174mLLgKDn7KMjJbpb0mFz1Ohwt-PCAiztVbh5Bv95DowuZXyCvBtOYsLbTwxUwE-GIfrInLI9GRXNfbTi1Yxp2-FpTgEs45nCq0UQpUzRHT_jhfTbgpfwn2eDjQIPNloZIXQMuegH1bDPGlX4nJVmD-H61wuvcRVtV_oSE; expires=Tue, 29-Dec-2020 21:20:13 GMT; path=/; domain=.google.com; HttpOnly'}
raw <urllib3.response.HTTPResponse object at 0x7fc3c0d190f0>
url http://www.google.com/
encoding ISO-8859-1
history []
reason OK
cookies <RequestsCookieJar[<Cookie 1P_JAR=2020-06-29-21 for .google.com/>, <Cookie NID=204=jAqS174mLLgKDn7KMjJbpb0mFz1Ohwt-PCAiztVbh5Bv95DowuZXyCvBtOYsLbTwxUwE-GIfrInLI9GRXNfbTi1Yxp2-FpTgEs45nCq0UQpUzRHT_jhfTbgpfwn2eDjQIPNloZIXQMuegH1bDPGlX4nJVmD-H61wuvcRVtV_oSE for .google.com/>]>
elapsed 0:00:05.139103
request <PreparedRequest [GET]>
connection <requests.adapters.HTTPAdapter object at 0x7fc3bff46208>



Second Request 0:00:00.303124
[Finished in 6.3s]
```
## System Information

    $ python -m requests.help

```
eonardo@leonardo-Acer:~/Desktop/Cheesecake$ python3 -m requests.help                                                                                        
{
  "chardet": {
    "version": "3.0.4"
  },
  "cryptography": {
    "version": ""
  },
  "idna": {
    "version": "2.6"
  },
  "implementation": {
    "name": "CPython",
    "version": "3.6.9"
  },
  "platform": {
    "release": "5.3.0-61-generic",
    "system": "Linux"
  },
  "pyOpenSSL": {
    "openssl_version": "",
    "version": null
  },
  "requests": {
    "version": "2.18.4"
  },
  "system_ssl": {
    "version": "1010100f"
  },
  "urllib3": {
    "version": "1.22"
  },
  "using_pyopenssl": false
}
```

This command is only available on Requests v2.16.4 and greater. Otherwise,
please provide some basic information about your system (Python version,
operating system, &c).


maybe you get the response headers in 5 seconds, but you get the content for more and more time(such as because of bad network)
timeout is only for connect, not the content

I discovered the problem. 
This problem just occur when using ipv6, when using ipv4,response comes in the right time.

I can observe the same behaviour on Fedora 32 via IPv6. This does not happen when disabling IPv6. Same thing seems to happen when using Arch but not Ubuntu. Adding the timeout parameter makes the request succeed. I propose reopening the issue.