picel failure on newer go 1.15

description

go tests are failing on the latest version of Go.

Still need to investigate. Using -race flag didn't detect any race condition, and this failure is happening with Mutual TLS.

go1.14.7-pass

$ go install golang.org/dl/go1.14.7
$ go1.14.7 download
$ go1.14.7 test ./...
ok  	github.com/henvic/httpretty	(cached)
?   	github.com/henvic/httpretty/example/client	[no test files]
?   	github.com/henvic/httpretty/example/httprepl	[no test files]
?   	github.com/henvic/httpretty/example/server	[no test files]
ok  	github.com/henvic/httpretty/internal/color	(cached)
ok  	github.com/henvic/httpretty/internal/header	(cached)

go1.15-failure

$ go version
go version go1.15 darwin/amd64
henvic at henvic in ~/projects/gocode/src/github.com/henvic/httpretty (master●)
$ go test ./...
2020/08/12 22:39:53 http: TLS handshake error from 127.0.0.1:59355: remote error: tls: bad certificate
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x40 pc=0x133264f]

goroutine 367 [running]:
github.com/henvic/httpretty.TestIncomingMutualTLS.func2(0xc0005b5500, 0xc00063e240, 0x27, 0xc0003e4180)
	/Users/henvic/projects/gocode/src/github.com/henvic/httpretty/server_test.go:1822 +0x14f
created by github.com/henvic/httpretty.TestIncomingMutualTLS
	/Users/henvic/projects/gocode/src/github.com/henvic/httpretty/server_test.go:1808 +0x7fc
FAIL	github.com/henvic/httpretty	0.574s
?   	github.com/henvic/httpretty/example/client	[no test files]
?   	github.com/henvic/httpretty/example/httprepl	[no test files]
?   	github.com/henvic/httpretty/example/server	[no test files]
ok  	github.com/henvic/httpretty/internal/color	(cached)
ok  	github.com/henvic/httpretty/internal/header	(cached)
FAIL