Support HTTP2 option

[shubham14bajpai]

This PR makes it possible to switch to send HTTP/2 requests when supported by the server.
Also found that connections is not passed to the attacker.Options struct while rebasing, fixed that as well 😃

Added a flag --http2 for switching to HTTP/2

mayadata:ali$ ./ali --help
Usage:
  ali [flags] <target URL>

Flags:
  -b, --body string         A request body to be sent.
  -B, --body-file string    The path to file whose content will be set as the http request body.
  -c, --connections int     Amount of maximum open idle connections per target host (default 10000
      --debug               Run in debug mode.
  -d, --duration duration   The amount of time to issue requests to the targets. Give 0s for an infinite attack. (default 10s)
  -H, --header strings      A request header to be sent. Can be used multiple times to send multiple headers.
      --http2               Issue HTTP/2 requests to servers which support it. (default true) (default true)
  -k, --keepalive           Use HTTP persistent connection. (default true)
  -M, --max-body int        Max bytes to capture from response bodies. Give -1 for no limit. (default -1)
  -W, --max-workers uint    Amount of maximum workers to spawn. (default 18446744073709551615)
  -m, --method string       An HTTP request method for each request. (default "GET")
  -r, --rate int            The request rate per second to issue against the targets. Give 0 then it will send requests as fast as possible. (default 50)
  -t, --timeout duration    The timeout for each request. 0s means to disable timeouts. (default 30s)
  -v, --version             Print the current version.
  -w, --workers uint        Amount of initial workers to spawn. (default 10)

Examples:
  ali --duration=10m --rate=100 http://host.xz

Author:
  Ryo Nakao <ryo@nakao.dev>

[codecov-commenter]

Codecov Report

Merging #49 into master will decrease coverage by 0.24%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master      #49      +/-   ##
==========================================
- Coverage   77.78%   77.55%   -0.23%     
==========================================
  Files           8        8              
  Lines         369      374       +5     
==========================================
+ Hits          287      290       +3     
- Misses         63       65       +2     
  Partials       19       19              

Impacted Files	Coverage Δ
attacker/attacker.go	67.50% <0.00%> (-1.94%)	⬇️
main.go	79.42% <0.00%> (+0.21%)	⬆️

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[nakabonne]

@shubham14bajpai Sorry for lacking a description. We need to make users possible to specify whether to enable HTTP/2 requests by flag like:

  --http2           Issue HTTP/2 requests to servers which support it. (default true)

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@fd4e04b). Click here to learn what that means.
The diff coverage is 92.86%.

@@            Coverage Diff            @@
##             master      #49   +/-   ##
=========================================
  Coverage          ?   77.72%           
=========================================
  Files             ?        8           
  Lines             ?      377           
  Branches          ?        0           
=========================================
  Hits              ?      293           
  Misses            ?       65           
  Partials          ?       19           

Impacted Files	Coverage Δ
attacker/attacker.go	67.50% <0.00%> (ø)
main.go	80.00% <100.00%> (ø)

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[shubham14bajpai]

@nakabonne Addressed the review comment and updated the PR description. PTAL.

[nakabonne]

Nice catch!

[nakabonne]

@shubham14bajpai Thanks for your contribution!