HTTP request hangs for some site

[arloan]

Checklist

• I've searched for similar issues.
• I'm using the latest version of HTTPie.

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What are the steps to reproduce the problem?

1. hit the "Try Online" button of the homepage of https://httpie.io/
2. input command 'http https://www.cmegroup.com' and hit Enter
3. the output hangs without response body

What is the expected result?
The response body text (web page source codes)

What happens instead?
None. Empty.

Debug output

Please re-run the command with --debug, then copy the entire command & output and paste both below:

~ $ http --debug https://www.cmegroup.com
HTTPie 2.4.0
Requests 2.26.0
Pygments 2.9.0
Python 3.7.6 (default, Jan 30 2020, 09:44:41) 
[GCC 9.2.1 20190827 (Red Hat 9.2.1-1)]
/usr/bin/python3
Linux 4.18.0-147.3.1.el8_1.x86_64

<Environment {'colors': 256,
 'config': {'default_options': ['--style=monokai']},
 'config_dir': PosixPath('/home/termible/.httpie'),
 'devnull': <property object at 0x7fbe6e995a10>,
 'is_windows': False,
 'log_error': <function Environment.log_error at 0x7fbe6e99a5f0>,
 'program_name': 'http',
 'stderr': <_io.TextIOWrapper name='<stderr>' mode='w' encoding='UTF-8'>,
 'stderr_isatty': True,
 'stdin': <_io.TextIOWrapper name='<stdin>' mode='r' encoding='UTF-8'>,
 'stdin_encoding': 'UTF-8',
 'stdin_isatty': True,
 'stdout': <_io.TextIOWrapper name='<stdout>' mode='w' encoding='UTF-8'>,
 'stdout_encoding': 'UTF-8',
 'stdout_isatty': True}>

>>> requests.request(**{'auth': None,
 'data': RequestJSONDataDict(),
 'headers': {'User-Agent': b'HTTPie/2.4.0'},
 'method': 'get',
 'params': <generator object MultiValueOrderedDict.items at 0x7fbe6e8ce4d0>,
 'url': 'https://www.cmegroup.com'})

Provide any additional information, screenshots, or code examples below:
The same problem occurs for https://www.nasdaq.com, while good for https://www.bing.com and many others.

[zhan9san]

This maybe network issue.

I verified all sites above work well with httpie.

[isidentical]

I also verified the website in the given reproducer works correctly on the latest revision. If you still experience this issue, please let us know.