Panic on darwin due to go-ieproxy

[Brcrwilliams]

github.com/mattn/go-ieproxy performs syscalls which can panic due to unexpected signal on MacOS: mattn/go-ieproxy#35

This issue is fixed in github.com/mattn/[email protected]. However, given #29 and #31, it's probably better to remove this dependency rather than upgrade it.

 fatal error: unexpected signal during runtime execution
 [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x7ff8054f94f6]
 
 runtime stack:
 runtime.throw({0x4fa5528, 0xffffffffffffffff})
       /Users/dcouture/.asdf/installs/golang/1.17.9/go/src/runtime/panic.go:1198 +0x71
 runtime.sigpanic()
       /Users/dcouture/.asdf/installs/golang/1.17.9/go/src/runtime/signal_unix.go:719 +0x396
 
 goroutine 1 [syscall, locked to thread]:
 runtime.cgocall(0x4c4b840, 0xc0001a17e0)
       /Users/dcouture/.asdf/installs/golang/1.17.9/go/src/runtime/cgocall.go:156 +0x5c fp=0xc0001a17b8 sp=0xc0001a1780 pc=0x400613c
 github.com/mattn/go-ieproxy._Cfunc_CFNumberGetValue(0x0, 0x9, 0xc0000425b8)
       _cgo_gotypes.go:191 +0x49 fp=0xc0001a17e0 sp=0xc0001a17b8 pc=0x431f0e9
 github.com/mattn/go-ieproxy.cfNumberGetGoInt.func1(0x431f4a9, 0x4c4b8e0)
       /Users/dcouture/.asdf/installs/golang/1.17.9/packages/pkg/mod/github.com/mattn/[email protected]/ieproxy_darwin.go:43 +0x59 fp=0xc0001a1820 sp=0xc0001a17e0 pc=0x431fb19
 github.com/mattn/go-ieproxy.cfNumberGetGoInt(0x0)
       /Users/dcouture/.asdf/installs/golang/1.17.9/packages/pkg/mod/github.com/mattn/[email protected]/ieproxy_darwin.go:43 +0x37 fp=0xc0001a1850 sp=0xc0001a1820 pc=0x431fa97
 github.com/mattn/go-ieproxy.writeConf()
       /Users/dcouture/.asdf/installs/golang/1.17.9/packages/pkg/mod/github.com/mattn/[email protected]/ieproxy_darwin.go:76 +0x275 fp=0xc0001a1940 sp=0xc0001a1850 pc=0x431ff95
 sync.(*Once).doSlow(0x7, 0xe)
       /Users/dcouture/.asdf/installs/golang/1.17.9/go/src/sync/once.go:68 +0xd2 fp=0xc0001a19a8 sp=0xc0001a1940 pc=0x40848f2
 sync.(*Once).Do(...)
       /Users/dcouture/.asdf/installs/golang/1.17.9/go/src/sync/once.go:59
 github.com/mattn/go-ieproxy.getConf(...)
       /Users/dcouture/.asdf/installs/golang/1.17.9/packages/pkg/mod/github.com/mattn/[email protected]/ieproxy_darwin.go:23
 github.com/mattn/go-ieproxy.GetConf(...)
       /Users/dcouture/.asdf/installs/golang/1.17.9/packages/pkg/mod/github.com/mattn/[email protected]/ieproxy.go:36
 github.com/mattn/go-ieproxy.proxyMiddleman()
       /Users/dcouture/.asdf/installs/golang/1.17.9/packages/pkg/mod/github.com/mattn/[email protected]/proxy_middleman_darwin.go:12 +0x57 fp=0xc0001a1a48 sp=0xc0001a19a8 pc=0x431e957
 github.com/mattn/go-ieproxy.GetProxyFunc(...)
       /Users/dcouture/.asdf/installs/golang/1.17.9/packages/pkg/mod/github.com/mattn/[email protected]/proxy_middleman.go:10
 github.com/Azure/azure-pipeline-go/pipeline.newDefaultHTTPClient()
       /Users/dcouture/.asdf/installs/golang/1.17.9/packages/pkg/mod/github.com/!azure/[email protected]/pipeline/core.go:208 +0x1d fp=0xc0001a1a80 sp=0xc0001a1a48 pc=0x4322e7d
 github.com/Azure/azure-pipeline-go/pipeline.init()
       /Users/dcouture/.asdf/installs/golang/1.17.9/packages/pkg/mod/github.com/!azure/[email protected]/pipeline/core.go:202 +0x19 fp=0xc0001a1aa0 sp=0xc0001a1a80 pc=0x4324f59
 runtime.doInit(0x5c8fdc0)
       /Users/dcouture/.asdf/installs/golang/1.17.9/go/src/runtime/proc.go:6498 +0x123 fp=0xc0001a1bd8 sp=0xc0001a1aa0 pc=0x40490c3
 runtime.doInit(0x5c94b20)
       /Users/dcouture/.asdf/installs/golang/1.17.9/go/src/runtime/proc.go:6475 +0x71 fp=0xc0001a1d10 sp=0xc0001a1bd8 pc=0x4049011
 runtime.doInit(0x5c8dc00)
       /Users/dcouture/.asdf/installs/golang/1.17.9/go/src/runtime/proc.go:6475 +0x71 fp=0xc0001a1e48 sp=0xc0001a1d10 pc=0x4049011
 runtime.doInit(0x5c93800)
       /Users/dcouture/.asdf/installs/golang/1.17.9/go/src/runtime/proc.go:6475 +0x71 fp=0xc0001a1f80 sp=0xc0001a1e48 pc=0x4049011
 runtime.main()
       /Users/dcouture/.asdf/installs/golang/1.17.9/go/src/runtime/proc.go:238 +0x1e6 fp=0xc0001a1fe0 sp=0xc0001a1f80 pc=0x403be06
 runtime.goexit()
       /Users/dcouture/.asdf/installs/golang/1.17.9/go/src/runtime/asm_amd64.s:1581 +0x1 fp=0xc0001a1fe8 sp=0xc0001a1fe0 pc=0x406dce1

[Brcrwilliams]

@zezha-msft @adreed-msft Could one of you look at this issue and also #29 and #31? This dependency seems quite problematic. I considered submitting a PR to replace it with http.ProxyFromEnvironment, but it looks like it might be here for Windows support? Do you know why this dependency is needed?