diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index e8c5eda..d79a1bf 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -28,7 +28,12 @@ make setup
 ### Running gaper in development
 
 ```
-make build && ./gaper --verbose --bin-name srv --build-path ./testdata/server --build-args="-ldflags=\"-X 'main.Version=v1.0.0'\""
+make build && \
+	./gaper \
+	--verbose \
+	--bin-name srv \
+	--build-path ./testdata/server \
+	--build-args="-ldflags=\"-X 'main.Version=v1.0.0'\""
 ```
 
 ### Running lint
diff --git a/builder_test.go b/builder_test.go
index 4ea52d9..28c3f71 100644
--- a/builder_test.go
+++ b/builder_test.go
@@ -44,7 +44,7 @@ func TestBuilderFailureBuild(t *testing.T) {
 	assert.Equal(t, err.Error(), "build failed with exit status 2\n"+
 		"# github.com/maxcnunes/gaper/testdata/build-failure\n"+
 		"./main.go:4:6: func main must have no arguments and no return values\n"+
-		"./main.go:5:1: missing return at end of function\n")
+		"./main.go:5:1: missing return\n")
 }
 
 func TestBuilderDefaultBinName(t *testing.T) {
diff --git a/cmd/gaper/main.go b/cmd/gaper/main.go
index b276a19..98bc072 100644
--- a/cmd/gaper/main.go
+++ b/cmd/gaper/main.go
@@ -9,9 +9,9 @@ import (
 
 // build info
 var (
-	// keep the version hardcoded because on installing it through "go get/install"
-	// it doesn't apply the build tags to override it. So, it is make easier for
-	// people using in that case to find out which version they are using
+	// Version is hardcoded because when installing it through "go get/install"
+	// the build tags are not available to override it.
+	// Update it after every release.
 	version = "1.0.3-dev"
 )
 
@@ -53,9 +53,7 @@ func main() {
 	}
 
 	exts := make(cli.StringSlice, len(gaper.DefaultExtensions))
-	for i := range gaper.DefaultExtensions {
-		exts[i] = gaper.DefaultExtensions[i]
-	}
+	copy(exts, gaper.DefaultExtensions)
 
 	// supported arguments
 	app.Flags = []cli.Flag{
diff --git a/gaper.go b/gaper.go
index 21ad6fd..d2200fb 100644
--- a/gaper.go
+++ b/gaper.go
@@ -7,6 +7,7 @@ import (
 	"os"
 	"os/signal"
 	"path/filepath"
+	"strings"
 	"syscall"
 	"time"
 
@@ -208,6 +209,15 @@ func setupConfig(cfg *Config) error {
 		cfg.WatchItems = append(cfg.WatchItems, cfg.BuildPath)
 	}
 
+	var extensions []string
+	for i := range cfg.Extensions {
+		values := strings.Split(cfg.Extensions[i], ",")
+		for _, e := range values {
+			extensions = append(extensions, e)
+		}
+	}
+	cfg.Extensions = extensions
+
 	return nil
 }
 
diff --git a/go.mod b/go.mod
index 80b585e..a875add 100644
--- a/go.mod
+++ b/go.mod
@@ -3,14 +3,21 @@ module github.com/maxcnunes/gaper
 go 1.13
 
 require (
+	github.com/alecthomas/gometalinter v3.0.0+incompatible // indirect
+	github.com/alecthomas/units v0.0.0-20211218093645-b94a6e3cc137 // indirect
 	github.com/davecgh/go-spew v1.1.0 // indirect
 	github.com/fatih/color v1.7.0
+	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 // indirect
 	github.com/mattn/go-colorable v0.0.9 // indirect
 	github.com/mattn/go-isatty v0.0.3 // indirect
 	github.com/mattn/go-shellwords v1.0.3
 	github.com/mattn/go-zglob v0.0.0-20180607075734-49693fbb3fe3
+	github.com/nicksnyder/go-i18n v1.10.1 // indirect
+	github.com/pelletier/go-toml v1.9.5 // indirect
 	github.com/stretchr/objx v0.1.1 // indirect
-	github.com/stretchr/testify v1.2.2
+	github.com/stretchr/testify v1.4.0
 	github.com/urfave/cli v1.22.2
 	golang.org/x/sys v0.0.0-20180616030259-6c888cc515d3 // indirect
+	gopkg.in/alecthomas/kingpin.v3-unstable v3.0.0-20191105091915-95d230a53780 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
 )
diff --git a/go.sum b/go.sum
index e720217..be78df0 100644
--- a/go.sum
+++ b/go.sum
@@ -1,10 +1,16 @@
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/alecthomas/gometalinter v3.0.0+incompatible h1:e9Zfvfytsw/e6Kd/PYd75wggK+/kX5Xn8IYDUKyc5fU=
+github.com/alecthomas/gometalinter v3.0.0+incompatible/go.mod h1:qfIpQGGz3d+NmgyPBqv+LSh50emm1pt72EtcX2vKYQk=
+github.com/alecthomas/units v0.0.0-20211218093645-b94a6e3cc137 h1:s6gZFSlWYmbqAuRjVTiNNhvNRfY2Wxp9nhfyel4rklc=
+github.com/alecthomas/units v0.0.0-20211218093645-b94a6e3cc137/go.mod h1:OMCwj8VM1Kc9e19TLln2VL61YJF0x1XFtfdL4JdbSyE=
 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/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/fatih/color v1.7.0 h1:DkWD4oS2D8LGGgTQ6IvwJJXSL5Vp2ffcQg58nFV38Ys=
 github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=
+github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 h1:El6M4kTTCOh6aBiKaUGG7oYTSPP8MxqL4YI3kZKwcP4=
+github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510/go.mod h1:pupxD2MaaD3pAXIBCelhxNneeOaAeabZDe5s4K6zSpQ=
 github.com/mattn/go-colorable v0.0.9 h1:UVL0vNpWh04HeJXV0KLcaT7r06gOH2l4OW6ddYRUIY4=
 github.com/mattn/go-colorable v0.0.9/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
 github.com/mattn/go-isatty v0.0.3 h1:ns/ykhmWi7G9O+8a448SecJU3nSMBXJfqQkl0upE1jI=
@@ -13,19 +19,32 @@ github.com/mattn/go-shellwords v1.0.3 h1:K/VxK7SZ+cvuPgFSLKi5QPI9Vr/ipOf4C1gN+nt
 github.com/mattn/go-shellwords v1.0.3/go.mod h1:3xCvwCdWdlDJUrvuMn7Wuy9eWs4pE8vqg+NOMyg4B2o=
 github.com/mattn/go-zglob v0.0.0-20180607075734-49693fbb3fe3 h1:GWnsQiFbiQ7lREZbKkiJC6xxbymvny8GKtpdkPxjB6o=
 github.com/mattn/go-zglob v0.0.0-20180607075734-49693fbb3fe3/go.mod h1:9fxibJccNxU2cnpIKLRRFA7zX7qhkJIQWBb449FYHOo=
+github.com/nicksnyder/go-i18n v1.10.1 h1:isfg77E/aCD7+0lD/D00ebR2MV5vgeQ276WYyDaCRQc=
+github.com/nicksnyder/go-i18n v1.10.1/go.mod h1:e4Di5xjP9oTVrC6y3C7C0HoSYXjSbhh/dU0eUV32nB4=
+github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
+github.com/pelletier/go-toml v1.9.5 h1:4yBQzkHv+7BHq2PQUZF3Mx0IYxG7LsP222s7Agd3ve8=
+github.com/pelletier/go-toml v1.9.5/go.mod h1:u1nR/EPcESfeI/szUZKdtJ0xRNbUoANCkoOuaOx1Y+c=
 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/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.1.1 h1:2vfRuCMp5sSVIDSqO8oNnWJq7mPa6KVP3iPIwFBuy8A=
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
+github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/urfave/cli v1.22.2 h1:gsqYFH8bb9ekPA12kRo0hfjngWQjkJPlN9R0N78BoUo=
 github.com/urfave/cli v1.22.2/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtXRu0=
 golang.org/x/sys v0.0.0-20180616030259-6c888cc515d3 h1:FCfAlbS73+IQQJktaKGHldMdL2bGDVpm+OrCEbVz1f4=
 golang.org/x/sys v0.0.0-20180616030259-6c888cc515d3/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+gopkg.in/alecthomas/kingpin.v3-unstable v3.0.0-20191105091915-95d230a53780 h1:CEBpW6C191eozfEuWdUmIAHn7lwlLxJ7HVdr2e2Tsrw=
+gopkg.in/alecthomas/kingpin.v3-unstable v3.0.0-20191105091915-95d230a53780/go.mod h1:3HH7i1SgMqlzxCcBmUHW657sD4Kvv9sC3HpL3YukzwA=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
+gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=