Repository: projectdiscovery/goflags (go)

Issue:
Flag support to convert file size with unit to bytes
Syntax
```go
func (flagSet *FlagSet) SizeVarP(...) *FlagData { ... }
func (flagSet *FlagSet) SizeVar(...) *FlagData { ... }
```
Description:
- SizeVar or SizeVarP has to convert the given fileSize with a unit (kb, mb, gb, or tb) to bytes.
- For example, '2kb' will be converted to 2048.
- If no unit is provided, it will fallback to mb. e.g: '2' will be converted to 2097152.

Pull request description:
Add support to convert file size with unit to bytes
closes #111 

Patch:
diff --git a/README.md b/README.md
index 8661634..2da88cb 100644
--- a/README.md
+++ b/README.md
@@ -46,6 +46,8 @@ The following types are supported by the goflags library. The `<name>P` suffix m
 | EnumVarP                 | Enum value with long short name                                     |
 | CallbackVar			   | Callback function as value with long name							 |
 | CallbackVarP			   | Callback function as value with long short name					 |
+| SizeVar                  | String value with long name                                         |
+| SizeVarP                 | String value with long short name                                   |
 
 
 ### String Slice Options
diff --git a/examples/basic/main.go b/examples/basic/main.go
index f684d09..c857027 100644
--- a/examples/basic/main.go
+++ b/examples/basic/main.go
@@ -8,10 +8,11 @@ import (
 )
 
 type Options struct {
-	name    string
-	Email   goflags.StringSlice
-	Phone   string
-	Address goflags.StringSlice
+	name     string
+	Email    goflags.StringSlice
+	Phone    string
+	Address  goflags.StringSlice
+	fileSize goflags.Size
 }
 
 func main() {
@@ -30,6 +31,7 @@ func main() {
 		flagSet.StringVarP(&testOptions.Phone, "phone", "ph", "", "phone of the user"),
 		flagSet.StringSliceVarP(&testOptions.Address, "address", "add", nil, "address of the user", goflags.StringSliceOptions),
 		flagSet.CallbackVarP(CheckUpdate, "update", "ut", "update this tool to latest version"),
+		flagSet.SizeVarP(&testOptions.fileSize, "max-size", "ms", "", "max file size"),
 	)
 
 	if err := flagSet.Parse(); err != nil {
diff --git a/go.mod b/go.mod
index b628639..6855fe4 100644
--- a/go.mod
+++ b/go.mod
@@ -5,17 +5,17 @@ go 1.18
 require (
 	github.com/cnf/structhash v0.0.0-20201127153200-e1b16c1ebc08
 	github.com/pkg/errors v0.9.1
-	github.com/stretchr/testify v1.8.1
+	github.com/stretchr/testify v1.8.3
 	golang.org/x/exp v0.0.0-20221019170559-20944726eadf
 	gopkg.in/yaml.v3 v3.0.1
 )
 
 require (
-	github.com/kr/pretty v0.3.1 // indirect
-	github.com/miekg/dns v1.1.50 // indirect
-	golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4 // indirect
-	golang.org/x/sys v0.5.0 // indirect
-	golang.org/x/tools v0.1.12 // indirect
+	github.com/miekg/dns v1.1.54 // indirect
+	github.com/projectdiscovery/blackrock v0.0.1 // indirect
+	golang.org/x/mod v0.8.0 // indirect
+	golang.org/x/sys v0.8.0 // indirect
+	golang.org/x/tools v0.6.0 // indirect
 )
 
 require (
@@ -23,9 +23,9 @@ require (
 	github.com/aymerick/douceur v0.2.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/gorilla/css v1.0.0 // indirect
-	github.com/microcosm-cc/bluemonday v1.0.21 // indirect
+	github.com/microcosm-cc/bluemonday v1.0.24 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/projectdiscovery/utils v0.0.4-0.20221214110533-9f95ee986a54
+	github.com/projectdiscovery/utils v0.0.35
 	github.com/saintfish/chardet v0.0.0-20120816061221-3af4cd4741ca // indirect
-	golang.org/x/net v0.7.0 // indirect
+	golang.org/x/net v0.10.0 // indirect
 )
diff --git a/go.sum b/go.sum
index 1802904..ae407b4 100644
--- a/go.sum
+++ b/go.sum
@@ -4,78 +4,38 @@ github.com/aymerick/douceur v0.2.0 h1:Mv+mAeH1Q+n9Fr+oyamOlAkUNPWPlA8PPGR0QAaYuP
 github.com/aymerick/douceur v0.2.0/go.mod h1:wlT5vV2O3h55X9m7iVYN0TBM0NH/MmbLnd30/FjWUq4=
 github.com/cnf/structhash v0.0.0-20201127153200-e1b16c1ebc08 h1:ox2F0PSMlrAAiAdknSRMDrAr8mfxPCfSZolH+/qQnyQ=
 github.com/cnf/structhash v0.0.0-20201127153200-e1b16c1ebc08/go.mod h1:pCxVEbcm3AMg7ejXyorUXi6HQCzOIBf7zEDVPtw0/U4=
-github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/gorilla/css v1.0.0 h1:BQqNyPTi50JCFMTw/b67hByjMVXZRwGha6wxVGkeihY=
 github.com/gorilla/css v1.0.0/go.mod h1:Dn721qIggHpt4+EFCcTLTU/vk5ySda2ReITrtgBl60c=
-github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
-github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
-github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
-github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
-github.com/microcosm-cc/bluemonday v1.0.21 h1:dNH3e4PSyE4vNX+KlRGHT5KrSvjeUkoNPwEORjffHJg=
-github.com/microcosm-cc/bluemonday v1.0.21/go.mod h1:ytNkv4RrDrLJ2pqlsSI46O6IVXmZOBBD4SaJyDwwTkM=
-github.com/miekg/dns v1.1.50 h1:DQUfb9uc6smULcREF09Uc+/Gd46YWqJd5DbpPE9xkcA=
-github.com/miekg/dns v1.1.50/go.mod h1:e3IlAVfNqAllflbibAZEWOXOQ+Ynzk/dDozDxY7XnME=
-github.com/pkg/diff v0.0.0-20210226163009-20ebb0f2a09e/go.mod h1:pJLUxLENpZxwdsKMEsNbx1VGcRFpLqf3715MtcvvzbA=
+github.com/microcosm-cc/bluemonday v1.0.24 h1:NGQoPtwGVcbGkKfvyYk1yRqknzBuoMiUrO6R7uFTPlw=
+github.com/microcosm-cc/bluemonday v1.0.24/go.mod h1:ArQySAMps0790cHSkdPEJ7bGkF2VePWH773hsJNSHf8=
+github.com/miekg/dns v1.1.54 h1:5jon9mWcb0sFJGpnI99tOMhCPyJ+RPVz5b63MQG0VWI=
+github.com/miekg/dns v1.1.54/go.mod h1:uInx36IzPl7FYnDcMeVWxj9byh7DutNykX4G9Sj60FY=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 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/projectdiscovery/utils v0.0.4-0.20221214110533-9f95ee986a54 h1:/fZvw6gT1fzdmMLMBBw75OrJ0Z6g7dulQrxM9FRp1qU=
-github.com/projectdiscovery/utils v0.0.4-0.20221214110533-9f95ee986a54/go.mod h1:PCwA5YuCYWPgHaGiZmr53/SA9iGQmAnw7DSHuhr8VPQ=
-github.com/rogpeppe/go-internal v1.9.0 h1:73kH8U+JUqXU8lRuOHeVHaa/SZPifC7BkcraZVejAe8=
-github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
+github.com/projectdiscovery/blackrock v0.0.1 h1:lHQqhaaEFjgf5WkuItbpeCZv2DUIE45k0VbGJyft6LQ=
+github.com/projectdiscovery/blackrock v0.0.1/go.mod h1:ANUtjDfaVrqB453bzToU+YB4cUbvBRpLvEwoWIwlTss=
+github.com/projectdiscovery/utils v0.0.35 h1:+ex4fbJlcbf/5/RXFZcI9SG0Fo27vxlwV5DP+fMLY+4=
+github.com/projectdiscovery/utils v0.0.35/go.mod h1:gyDuJpCGPHN6Lyo3O8PAkTxf88iiAxRZyaMFMrXV0z4=
 github.com/saintfish/chardet v0.0.0-20120816061221-3af4cd4741ca h1:NugYot0LIVPxTvN8n+Kvkn6TrbMyxQiuvKdEwFdR9vI=
 github.com/saintfish/chardet v0.0.0-20120816061221-3af4cd4741ca/go.mod h1:uugorj2VCxiV1x+LzaIdVa9b4S4qGAcH6cbhh4qVxOU=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
-github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
-github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
-github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
-github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-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=
+github.com/stretchr/testify v1.8.3 h1:RP3t2pwF7cMEbC1dqtB6poj3niw/9gnV4Cjg5oW5gtY=
+github.com/stretchr/testify v1.8.3/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 golang.org/x/exp v0.0.0-20221019170559-20944726eadf h1:nFVjjKDgNY37+ZSYCJmtYf7tOlfQswHqplG2eosjOMg=
 golang.org/x/exp v0.0.0-20221019170559-20944726eadf/go.mod h1:cyybsKvd6eL0RnXn6p/Grxp8F5bW7iYuBgsNCOHpMYE=
-golang.org/x/mod v0.4.2/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4 h1:6zppjxzCulZykYSLyVDYbneBfbaBIQPYMevg0bEwv2s=
-golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4/go.mod h1:p54w0d4576C0XHj96bSt6lcn1PtDYWL6XObtHCRCNQM=
-golang.org/x/net v0.0.0-20210726213435-c6fcb2dbf985/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
-golang.org/x/net v0.7.0 h1:rJrUqqhjsgNp7KqAIc25s9pZnjU7TUcSY7HcVZjdn1g=
-golang.org/x/net v0.7.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
-golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4 h1:uVc8UZUe6tr40fFVnUP5Oj+veunVezqYl9z7DYw9xzw=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210330210617-4fbd30eecc44/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210510120138-977fb7262007/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.5.0 h1:MUK/U/4lj1t1oPg0HfuXDN/Z1wv31ZJ/YcPiGccS4DU=
-golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
-golang.org/x/tools v0.1.6-0.20210726203631-07bc1bf47fb2/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
-golang.org/x/tools v0.1.12 h1:VveCTK38A2rkS8ZqFY25HIDFscX5X9OoEhJd3quQmXU=
-golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/mod v0.8.0 h1:LUYupSeNrTNCGzR/hVBk2NHZO4hXcVaW1k4Qx7rjPx8=
+golang.org/x/mod v0.8.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
+golang.org/x/net v0.10.0 h1:X2//UzNDwYmtCLn7To6G58Wr6f5ahEAQgKNzv9Y951M=
+golang.org/x/net v0.10.0/go.mod h1:0qNGK6F8kojg2nk9dLZ2mShWaEBan6FAoqfSigmmuDg=
+golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
+golang.org/x/sys v0.8.0 h1:EBmGv8NaZBZTWvrbjNoL6HVt+IVy3QDQpJs7VRIw3tU=
+golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/tools v0.6.0 h1:BOw41kyTf3PuCW1pVQf8+Cyg8pMlkYB1oo9iJ6D/lKM=
+golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/size_var.go b/size_var.go
new file mode 100644
index 0000000..03b72b5
--- /dev/null
+++ b/size_var.go
@@ -0,0 +1,57 @@
+package goflags
+
+import (
+	"fmt"
+	"strconv"
+
+	fileutil "github.com/projectdiscovery/utils/file"
+)
+
+type Size int
+
+func (s *Size) Set(size string) error {
+	sizeInBytes, err := fileutil.FileSizeToByteLen(size)
+	if err != nil {
+		return err
+	}
+	*s = Size(sizeInBytes)
+	return nil
+}
+
+func (s *Size) String() string {
+	return strconv.Itoa(int(*s))
+}
+
+// SizeVar converts the given fileSize with a unit (kb, mb, gb, or tb) to bytes.
+// For example, '2kb' will be converted to 2048.
+// If no unit is provided, it will fallback to mb. e.g: '2' will be converted to 2097152.
+func (flagSet *FlagSet) SizeVar(field *Size, long string, defaultValue string, usage string) *FlagData {
+	return flagSet.SizeVarP(field, long, "", defaultValue, usage)
+}
+
+// SizeVarP converts the given fileSize with a unit (kb, mb, gb, or tb) to bytes.
+// For example, '2kb' will be converted to 2048.
+// If no unit is provided, it will fallback to mb. e.g: '2' will be converted to 2097152.
+func (flagSet *FlagSet) SizeVarP(field *Size, long, short string, defaultValue string, usage string) *FlagData {
+	if field == nil {
+		panic(fmt.Errorf("field cannot be nil for flag -%v", long))
+	}
+	if defaultValue != "" {
+		if err := field.Set(defaultValue); err != nil {
+			panic(fmt.Errorf("failed to set default value for flag -%v: %v", long, err))
+		}
+	}
+	flagData := &FlagData{
+		usage:        usage,
+		long:         long,
+		defaultValue: defaultValue,
+	}
+	if short != "" {
+		flagData.short = short
+		flagSet.CommandLine.Var(field, short, usage)
+		flagSet.flagKeys.Set(short, flagData)
+	}
+	flagSet.CommandLine.Var(field, long, usage)
+	flagSet.flagKeys.Set(long, flagData)
+	return flagData
+}


Test patch:
diff --git a/.github/workflows/build-test.yml b/.github/workflows/build-test.yml
index 7033c78..d2467fd 100644
--- a/.github/workflows/build-test.yml
+++ b/.github/workflows/build-test.yml
@@ -12,7 +12,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v3
         with:
-          go-version: 1.18
+          go-version: 1.20.x
 
       - name: Check out code
         uses: actions/checkout@v3
diff --git a/.github/workflows/lint-test.yml b/.github/workflows/lint-test.yml
index 95bbdce..b8aabe2 100644
--- a/.github/workflows/lint-test.yml
+++ b/.github/workflows/lint-test.yml
@@ -13,7 +13,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v3
         with:
-          go-version: 1.18
+          go-version: 1.20.x
       - name: Run golangci-lint
         uses: golangci/golangci-lint-action@v3.3.0
         with:
diff --git a/size_var_test.go b/size_var_test.go
new file mode 100644
index 0000000..c7cd5a3
--- /dev/null
+++ b/size_var_test.go
@@ -0,0 +1,57 @@
+package goflags
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSizeVar(t *testing.T) {
+	t.Run("valid-size", func(t *testing.T) {
+		var fileSize Size
+		flagSet := NewFlagSet()
+		flagSet.CreateGroup("Config", "Config",
+			flagSet.SizeVarP(&fileSize, "max-size", "ms", "", "max size of the file"),
+		)
+		os.Args = []string{
+			os.Args[0],
+			"-max-size", "2kb",
+		}
+		err := flagSet.Parse()
+		assert.Nil(t, err)
+		assert.Equal(t, Size(2048), fileSize)
+		tearDown(t.Name())
+	})
+
+	t.Run("default-value", func(t *testing.T) {
+		var fileSize Size
+		flagSet := NewFlagSet()
+		flagSet.CreateGroup("Config", "Config",
+			flagSet.SizeVarP(&fileSize, "max-size", "ms", "2kb", "max size of the file"),
+		)
+		os.Args = []string{
+			os.Args[0],
+		}
+		err := flagSet.Parse()
+		assert.Nil(t, err)
+		assert.Equal(t, Size(2048), fileSize)
+		tearDown(t.Name())
+	})
+
+	t.Run("without-unit", func(t *testing.T) {
+		var fileSize Size
+		err := fileSize.Set("2")
+		assert.Nil(t, err)
+		assert.Equal(t, Size(2097152), fileSize)
+		tearDown(t.Name())
+	})
+
+	t.Run("invalid-size-unit", func(t *testing.T) {
+		var fileSize Size
+		err := fileSize.Set("2kilobytes")
+		assert.NotNil(t, err)
+		assert.ErrorContains(t, err, "parse error")
+		tearDown(t.Name())
+	})
+}