Running blogrenderer benchmark test causes panic

[logan-connolly]

Hey @quii,

First off, thanks so much for this amazing learning resource. It has helped me so much!

As the title suggest, running BenchmarkRender causes a panic. It seems that the blogrender unit tests run fine because postRenderer.Render is only called only once, but as soon as you call it again, you can reproduce the panic.

Traceback

learn-go-with-tests/blogrenderer  main 🐹 v1.20
❯ go test -bench=.
goos: linux
goarch: amd64
pkg: github.com/quii/learn-go-with-tests/blogrenderer
cpu: Intel(R) Core(TM) i7-10710U CPU @ 1.10GHz
BenchmarkRender-12      panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x30 pc=0x5c53d1]

goroutine 35 [running]:
github.com/gomarkdown/markdown/parser.(*Parser).finalize(...)
        /home/archie/go/pkg/mod/github.com/gomarkdown/markdown@v0.0.0-20211212230626-5af6ad2f47df/parser/parser.go:206
github.com/gomarkdown/markdown/parser.(*Parser).addChild(0xc0000a6000, {0x6dc6b0?, 0xc000028900})
        /home/archie/go/pkg/mod/github.com/gomarkdown/markdown@v0.0.0-20211212230626-5af6ad2f47df/parser/parser.go:211 +0x71
github.com/gomarkdown/markdown/parser.(*Parser).addBlock(0xc0000a6000, {0x6dc6b0, 0xc000028900})
        /home/archie/go/pkg/mod/github.com/gomarkdown/markdown@v0.0.0-20211212230626-5af6ad2f47df/parser/block.go:392 +0x105
github.com/gomarkdown/markdown/parser.(*Parser).renderParagraph(0xc000018320?, {0xc000018320, 0x10?, 0x10})
        /home/archie/go/pkg/mod/github.com/gomarkdown/markdown@v0.0.0-20211212230626-5af6ad2f47df/parser/block.go:1548 +0x10a
github.com/gomarkdown/markdown/parser.(*Parser).paragraph(0xc0000a6000, {0xc000018320, 0xe, 0x10})
        /home/archie/go/pkg/mod/github.com/gomarkdown/markdown@v0.0.0-20211212230626-5af6ad2f47df/parser/block.go:1711 +0x53f
github.com/gomarkdown/markdown/parser.(*Parser).block(0xc0000a6000, {0xc000018320?, 0xc000211ad8?, 0x5e57a4?})
        /home/archie/go/pkg/mod/github.com/gomarkdown/markdown@v0.0.0-20211212230626-5af6ad2f47df/parser/block.go:373 +0xf1c
github.com/gomarkdown/markdown/parser.(*Parser).Parse(0xc0000a6000, {0xc000018320?, 0x65d000?, 0xc0000288a0?})
        /home/archie/go/pkg/mod/github.com/gomarkdown/markdown@v0.0.0-20211212230626-5af6ad2f47df/parser/parser.go:272 +0x3e
github.com/gomarkdown/markdown.Parse({0xc000018320?, 0x0?, 0x99?}, 0x65d000?)
        /home/archie/go/pkg/mod/github.com/gomarkdown/markdown@v0.0.0-20211212230626-5af6ad2f47df/markdown.go:53 +0x65
github.com/gomarkdown/markdown.ToHTML({0xc000018320?, 0x68a75c?, 0xe?}, 0x6893de?, {0x0, 0x0})
        /home/archie/go/pkg/mod/github.com/gomarkdown/markdown@v0.0.0-20211212230626-5af6ad2f47df/markdown.go:77 +0x45
github.com/quii/learn-go-with-tests/blogrenderer.newPostVM(...)
        /home/archie/projects/work/learn-go-with-tests-source/blogrenderer/renderer.go:52
github.com/quii/learn-go-with-tests/blogrenderer.(*PostRenderer).Render(0xc000060300, {0x6da980, 0x88df00}, {{0x689512, 0xb}, {0x68d96e, 0x15}, {0x68a75c, 0xe}, {0xc00006c000, ...}})
        /home/archie/projects/work/learn-go-with-tests-source/blogrenderer/renderer.go:37 +0x125
github.com/quii/learn-go-with-tests/blogrenderer_test.BenchmarkRender(0xc00010a280)
        /home/archie/projects/work/learn-go-with-tests-source/blogrenderer/renderer_test.go:68 +0x1b3
testing.(*B).runN(0xc00010a280, 0x64)
        /usr/lib/go/src/testing/benchmark.go:193 +0x102
testing.(*B).launch(0xc00010a280)
        /usr/lib/go/src/testing/benchmark.go:334 +0x1c5
created by testing.(*B).doBench
        /usr/lib/go/src/testing/benchmark.go:284 +0x6c
exit status 2
FAIL    github.com/quii/learn-go-with-tests/blogrenderer        0.007s

Hope this helps and thanks again for all your hard work!