fix: ClientTrace nil pointer panic

[boekkooi-impossiblecloud]

Good day,

During our peak hours we have noticed the following invalid memory address or nil pointer dereference which causes pod restarts. The goal of this PR is to avoid these panics.

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x142d033]

goroutine 6941 [running]:
go.opentelemetry.io/contrib/instrumentation/net/http/httptrace/otelhttptrace.(*clientTracer).got100Continue(0x0?)
        /app/vendor/go.opentelemetry.io/contrib/instrumentation/net/http/httptrace/otelhttptrace/clienttrace.go:363 +0x33
net/http.(*persistConn).readResponse(0xc004acea20, {{}, 0xc00c31e370, 0xc006d058f0, 0x0, 0xc006d05810, 0xc006d05880}, 0xc006893100)
        /usr/local/go/src/net/http/transport.go:2470 +0xfd
net/http.(*persistConn).readLoop(0xc004acea20)
        /usr/local/go/src/net/http/transport.go:2290 +0x2a6
created by net/http.(*Transport).dialConn in goroutine 6933
        /usr/local/go/src/net/http/transport.go:1944 +0x172f

Thanks for reviewing and let me know what you think.
Have a great day!

[dmathieu]

Would it make sense to use a noop span instead ?

[boekkooi-impossiblecloud]

@dmathieu I tried that first but that makes the if statements (in wroteHeaders and wroteHeaderField) that currently check for nil harder, so I went for sticking to the existing method of checking for nil

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 9 lines in your changes missing coverage. Please review.

Project coverage is 81.5%. Comparing base (a39bd91) to head (5be7225).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...on/net/http/httptrace/otelhttptrace/clienttrace.go	25.0%	7 Missing and 2 partials ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #7464   +/-   ##
=====================================
  Coverage   81.4%   81.5%           
=====================================
  Files        198     198           
  Lines      17946   17952    +6     
=====================================
+ Hits       14621   14634   +13     
+ Misses      2927    2918    -9     
- Partials     398     400    +2     

Files with missing lines	Coverage Δ
...on/net/http/httptrace/otelhttptrace/clienttrace.go	82.8% <25.0%> (+3.2%)	⬆️

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[pellared]

Can you please resolve the conflict?

[boekkooi-impossiblecloud]

@pellared Sorry I had to rebase (and I squashed the changes as coffee detox made me fetch the wrong remote 🙈)

Need to review again.

[boekkooi-impossiblecloud]

Thanks @pellared and @dmathieu for reviewing and sorry for the back and forth on this one.

[pellared]

Thanks @pellared and @dmathieu for reviewing and sorry for the back and forth on this one.

Everything is fine. Thanks a lot for your contribution! ❤️