tests failing

[marten-seemann]

Using Go 1.15.5 on OSX:

❯ go test
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x28 pc=0x116535d]

goroutine 907 [running]:
github.com/multiformats/go-multistream.(*rwcStrict).Write(0xc0001f5760, 0xc0000e0000, 0x14, 0x1000, 0xc0003902f1, 0x1, 0x1)
	/Users/marten/src/go/src/github.com/multiformats/go-multistream/multistream_test.go:41 +0xdd
bufio.(*Writer).Flush(0xc0000d4680, 0xc0000d4680, 0xc000388fa0)
	/usr/local/Cellar/go/1.15.5/libexec/src/bufio/bufio.go:607 +0x7b
github.com/multiformats/go-multistream.delimWriteBuffered(0x1708fd0, 0xc0001f5760, 0xc000388fa0, 0x12, 0x12, 0x0, 0x0)
	/Users/marten/src/go/src/github.com/multiformats/go-multistream/multistream.go:81 +0xf4
github.com/multiformats/go-multistream.(*MultistreamMuxer).NegotiateLazy.func1()
	/Users/marten/src/go/src/github.com/multiformats/go-multistream/multistream.go:227 +0x13c
sync.(*Once).doSlow(0xc0000fd620, 0xc00038c840)
	/usr/local/Cellar/go/1.15.5/libexec/src/sync/once.go:66 +0xec
sync.(*Once).Do(0xc0000fd620, 0xc00038c840)
	/usr/local/Cellar/go/1.15.5/libexec/src/sync/once.go:57 +0x45
created by github.com/multiformats/go-multistream.(*MultistreamMuxer).NegotiateLazy
	/Users/marten/src/go/src/github.com/multiformats/go-multistream/multistream.go:222 +0x1ec
exit status 2
FAIL	github.com/multiformats/go-multistream	0.563s