panic: runtime error: invalid memory address or nil pointer dereference

[lifubang]

root@iZ2ze75xet9v7jhynivwhdZ:~/gocode/src/github.com/genuinetools/riddler# ./riddler alpine
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x73e36e]

goroutine 1 [running]:
github.com/genuinetools/riddler/parse.Config(0xc42033c2c0, 0xa7f978, 0x0, 0x0, 0xc42035a000, 0xc42032a200, 0x82e593, 0x5, 0x82e4c6, 0x5, ...)
	/root/gocode/src/github.com/genuinetools/riddler/parse/config.go:175 +0x1fe
main.main.func2(0x879f60, 0xc4201b5b90, 0xc420098010, 0x1, 0x1, 0x0, 0x7)
	/root/gocode/src/github.com/genuinetools/riddler/main.go:154 +0x3f1
github.com/genuinetools/riddler/vendor/github.com/genuinetools/pkg/cli.(*Program).runAction(0xc4200d5d00, 0x879f60, 0xc4201b5b90, 0xc420098000, 0x2, 0x2, 0x0, 0x1, 0x4f6b27)
	/root/gocode/src/github.com/genuinetools/riddler/vendor/github.com/genuinetools/pkg/cli/cli.go:219 +0x159
github.com/genuinetools/riddler/vendor/github.com/genuinetools/pkg/cli.(*Program).run(0xc4200d5d00, 0x879f60, 0xc4201b5b90, 0xc420098000, 0x2, 0x2, 0x879f60, 0xc4201b5b90, 0x412008)
	/root/gocode/src/github.com/genuinetools/riddler/vendor/github.com/genuinetools/pkg/cli/cli.go:135 +0x142
github.com/genuinetools/riddler/vendor/github.com/genuinetools/pkg/cli.(*Program).Run(0xc4200d5d00)
	/root/gocode/src/github.com/genuinetools/riddler/vendor/github.com/genuinetools/pkg/cli/cli.go:88 +0x170
main.main()
	/root/gocode/src/github.com/genuinetools/riddler/main.go:170 +0x3dd

while the container named alpine is from:

docker run --name alpine alpine date

and docker inspect alpine | grep Swap:

            "MemorySwap": 0,
            "MemorySwappiness": null,

The error raised because the MemorySwappiness field is null.