diff --git a/go.mod b/go.mod
index fb6adf5..fb891ba 100644
--- a/go.mod
+++ b/go.mod
@@ -5,13 +5,12 @@ go 1.17
 require (
 	github.com/lixiangzhong/dnsutil v1.4.0
 	github.com/miekg/dns v1.1.46
-	github.com/urfave/cli/v2 v2.3.0
+	github.com/urfave/cli/v2 v2.4.0
 )
 
 require (
-	github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d // indirect
-	github.com/russross/blackfriday/v2 v2.0.1 // indirect
-	github.com/shurcooL/sanitized_anchor_name v1.0.0 // indirect
+	github.com/cpuguy83/go-md2man/v2 v2.0.1 // indirect
+	github.com/russross/blackfriday/v2 v2.1.0 // indirect
 	golang.org/x/mod v0.4.2 // indirect
 	golang.org/x/net v0.0.0-20210726213435-c6fcb2dbf985 // indirect
 	golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c // indirect
diff --git a/go.sum b/go.sum
index ece2c0b..2046b98 100644
--- a/go.sum
+++ b/go.sum
@@ -1,19 +1,15 @@
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
-github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d h1:U+s90UTSYgptZMwQh2aRr3LuazLJIa+Pg3Kc1ylSYVY=
-github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
+github.com/cpuguy83/go-md2man/v2 v2.0.1 h1:r/myEWzV9lfsM1tFLgDyu0atFtJ1fXn261LKYj/3DxU=
+github.com/cpuguy83/go-md2man/v2 v2.0.1/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/lixiangzhong/dnsutil v1.4.0 h1:S75ND4O8IbNhVdaP/Bn+3YHXPYvt6jpeqy3Yyr+iUNY=
 github.com/lixiangzhong/dnsutil v1.4.0/go.mod h1:hQj5Vdv9+/m5GZxu75Hp4SMPeYV3JZUABlUadwNVFmk=
 github.com/miekg/dns v1.1.40/go.mod h1:KNUDUusw/aVsxyTYZM1oqvCicbwhgbNgztCETuNZ7xM=
 github.com/miekg/dns v1.1.46 h1:uzwpxRtSVxtcIZmz/4Uz6/Rn7G11DvsaslXoy5LxQio=
 github.com/miekg/dns v1.1.46/go.mod h1:e3IlAVfNqAllflbibAZEWOXOQ+Ynzk/dDozDxY7XnME=
-github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
-github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/russross/blackfriday/v2 v2.0.1 h1:lPqVAte+HuHNfhJ/0LC98ESWRz8afy9tM/0RK8m9o+Q=
-github.com/russross/blackfriday/v2 v2.0.1/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
-github.com/shurcooL/sanitized_anchor_name v1.0.0 h1:PdmoCO6wvbs+7yrJyMORt4/BmY5IYyJwS/kOiWx8mHo=
-github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeVRXNmyL/1OwPU0+IJeTBvfc=
-github.com/urfave/cli/v2 v2.3.0 h1:qph92Y649prgesehzOrQjdWyxFOp/QVM+6imKHad91M=
-github.com/urfave/cli/v2 v2.3.0/go.mod h1:LJmUH05zAU44vOAcrfzZQKsZbVcdbOG8rtL3/XcUArI=
+github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf35Ld67mk=
+github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/urfave/cli/v2 v2.4.0 h1:m2pxjjDFgDxSPtO8WSdbndj17Wu2y8vOT86wE/tjr+I=
+github.com/urfave/cli/v2 v2.4.0/go.mod h1:NX9W0zmTvedE5oDoOMs2RTC8RvdK98NTYZE5LbaEYPg=
 github.com/yuin/goldmark v1.3.5/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
@@ -53,4 +49,4 @@ golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8T
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.2.3/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=