diff --git a/.gitignore b/.gitignore
index cdebd88..ba1e28a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 expvarmon
 *.swp
+.idea/
diff --git a/average.go b/average.go
index 7adc0f7..53bd39c 100644
--- a/average.go
+++ b/average.go
@@ -5,7 +5,7 @@ import (
 )
 
 func averageJason(array []*jason.Value) float64 {
-	var arr []float64
+	arr := make([]float64, 0, len(array))
 	for _, v := range array {
 		val, _ := v.Float64()
 		arr = append(arr, val)
diff --git a/expvars.go b/expvars.go
index 59e23fa..90637b7 100644
--- a/expvars.go
+++ b/expvars.go
@@ -23,8 +23,8 @@ func getBasicAuthEnv() (user, password string) {
 	return os.Getenv("HTTP_USER"), os.Getenv("HTTP_PASSWORD")
 }
 
-// FetchExpvar fetches expvar by http for the given addr (host:port)
-func FetchExpvar(u url.URL) (*Expvar, error) {
+// FetchExpvar fetches expvar by http for the given addr (host:port).
+func FetchExpvar(u url.URL, headers map[string]string) (*Expvar, error) {
 	e := &Expvar{&jason.Object{}}
 	client := &http.Client{
 		Timeout: 1 * time.Second, // TODO: make it configurable or left default?
@@ -34,6 +34,10 @@ func FetchExpvar(u url.URL) (*Expvar, error) {
 	req.URL = &u
 	req.Host = u.Host
 
+	for k, v := range headers {
+		req.Header.Add(k, v)
+	}
+
 	if user, pass := getBasicAuthEnv(); user != "" && pass != "" {
 		req.SetBasicAuth(user, pass)
 	}
diff --git a/go.mod b/go.mod
index 9ae1632..ca6441d 100644
--- a/go.mod
+++ b/go.mod
@@ -1,5 +1,7 @@
 module github.com/divan/expvarmon
 
+go 1.15
+
 require (
 	github.com/antonholmquist/jason v1.0.0
 	github.com/bsiegert/ranges v0.0.0-20111221115336-19303dc7aa63
diff --git a/go.sum b/go.sum
index df539e3..833b7ac 100644
--- a/go.sum
+++ b/go.sum
@@ -2,13 +2,10 @@ github.com/antonholmquist/jason v1.0.0 h1:Ytg94Bcf1Bfi965K2q0s22mig/n4eGqEij/atE
 github.com/antonholmquist/jason v1.0.0/go.mod h1:+GxMEKI0Va2U8h3os6oiUAetHAlGMvxjdpAH/9uvUMA=
 github.com/bsiegert/ranges v0.0.0-20111221115336-19303dc7aa63 h1:FxdkNGQyRwwk94rJ+IMNrTjv864XzT93/cvk7UpMM38=
 github.com/bsiegert/ranges v0.0.0-20111221115336-19303dc7aa63/go.mod h1:8z71/aZjDHLs4ihK/5nD5wZVQxm/W4eRDnxQZcJmVD4=
-github.com/cjbassi/drawille-go v0.0.0-20190126131713-27dc511fe6fd h1:XtfPmj9tQRilnrEmI1HjQhxXWRhEM+m8CACtaMJE/kM=
-github.com/cjbassi/drawille-go v0.0.0-20190126131713-27dc511fe6fd/go.mod h1:vjcQJUZJYD3MeVGhtZXSMnCHfUNZxsyYzJt90eCYxK4=
+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/gizak/termui v0.0.0-20181228210747-b136f68f55f1 h1:TCe+sQ3zOPa8KNePfjrb5Pix5FPa44WsiiCzsYv0Yts=
 github.com/gizak/termui v0.0.0-20181228210747-b136f68f55f1/go.mod h1:W48Llfv3G9PIK3TQjqynxzC9mP4HUcAn/6vlDWekq9k=
-github.com/gizak/termui v0.0.0-20190202061602-5ece2b7178ff h1:md8xjZ5dOJsdTnDXsnbu2W9WLBpZ3yh8ebRad+i2bQY=
-github.com/gizak/termui v0.0.0-20190202061602-5ece2b7178ff/go.mod h1:TISPFiAGKVhyNxElRxDknJ+HzcUyO7sAJCsc8dfAe+M=
 github.com/mattn/go-runewidth v0.0.2/go.mod h1:LwmH8dsx7+W8Uxz3IHJYH5QSwggIsqBzpuz5H//U1FU=
 github.com/mattn/go-runewidth v0.0.4 h1:2BvfKmzob6Bmd4YsL0zygOqfdFnK7GR4QL06Do4/p7Y=
 github.com/mattn/go-runewidth v0.0.4/go.mod h1:LwmH8dsx7+W8Uxz3IHJYH5QSwggIsqBzpuz5H//U1FU=
@@ -17,11 +14,10 @@ github.com/mitchellh/go-wordwrap v1.0.0 h1:6GlHJ/LTGMrIJbwgdqdl2eEH8o+Exx/0m8ir9
 github.com/mitchellh/go-wordwrap v1.0.0/go.mod h1:ZXFpozHsX6DPmq2I0TCekCxypsnAUbP2oI0UX1GXzOo=
 github.com/nsf/termbox-go v0.0.0-20180613055208-5c94acc5e6eb h1:YahEjAGkJtCrkqgVHhX6n8ZX+CZ3hDRL9fjLYugLfSs=
 github.com/nsf/termbox-go v0.0.0-20180613055208-5c94acc5e6eb/go.mod h1:IuKpRQcYE1Tfu+oAQqaLisqDeXgjyyltCfsaoYN18NQ=
-github.com/nsf/termbox-go v0.0.0-20190121233118-02980233997d h1:x3S6kxmy49zXVVyhcnrFqxvNVCBPb2KZ9hV2RBdS840=
-github.com/nsf/termbox-go v0.0.0-20190121233118-02980233997d/go.mod h1:IuKpRQcYE1Tfu+oAQqaLisqDeXgjyyltCfsaoYN18NQ=
+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/pyk/byten v0.0.0-20140925233358-f847a130bf6d h1:/0nqYrqVyPTVDT2jPx9z9BZ+ItJWlWA9VITUGvNaZkI=
 github.com/pyk/byten v0.0.0-20140925233358-f847a130bf6d/go.mod h1:El8LdwAxb76Ih0mRmpu9uMVq+ajiqGSxmYiUe+nSr+w=
+github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
-golang.org/x/arch v0.0.0-20181203225421-5a4828bb7045/go.mod h1:cYlCBUl1MsqxdiKgmc4uh7TxZfWSFLOGSRR090WDxt8=
 golang.org/x/net v0.0.0-20180801234040-f4c29de78a2a/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
diff --git a/main.go b/main.go
index 0787d1c..9095d07 100644
--- a/main.go
+++ b/main.go
@@ -11,6 +11,17 @@ import (
 	"github.com/gizak/termui"
 )
 
+type arrayFlags []string
+
+func (i *arrayFlags) String() string {
+	return "list of custom headers to pass to the endpoint"
+}
+
+func (i *arrayFlags) Set(value string) error {
+	*i = append(*i, value)
+	return nil
+}
+
 var (
 	interval = flag.Duration("i", 5*time.Second, "Polling interval")
 	urls     = flag.String("ports", "", "Ports/URLs for accessing services expvars (start-end,port2,port3,https://host:port)")
@@ -18,9 +29,11 @@ var (
 	dummy    = flag.Bool("dummy", false, "Use dummy (console) output")
 	self     = flag.Bool("self", false, "Monitor itself")
 	endpoint = flag.String("endpoint", DefaultEndpoint, "URL endpoint for expvars")
+	headers  arrayFlags
 )
 
 func main() {
+	flag.Var(&headers, "headers", "Custom headers to pass onto application")
 	flag.Usage = Usage
 	flag.Parse()
 
@@ -55,6 +68,7 @@ func main() {
 	data := NewUIData(vars)
 	for _, port := range ports {
 		service := NewService(port, vars)
+		service.CustomHeaders = ParseHeaders(headers)
 		data.Services = append(data.Services, service)
 	}
 
@@ -106,7 +120,7 @@ func UpdateAll(ui UI, data *UIData) {
 	ui.Update(*data)
 }
 
-// Usage reimplements flag.Usage
+// Usage reimplements flag.Usage.
 func Usage() {
 	progname := os.Args[0]
 	fmt.Fprintf(os.Stderr, "Usage of %s:\n", progname)
@@ -114,10 +128,11 @@ func Usage() {
 	fmt.Fprintf(os.Stderr, `
 Examples:
 	%s -ports="80"
+	%s -headers="X-Custom-Header: Foo" -headers="X-Another-Header: Bar" -ports="80"
 	%s -ports="23000-23010,http://example.com:80-81" -i=1m
 	%s -ports="80,remoteapp:80" -vars="mem:memstats.Alloc,duration:Response.Mean,Counter"
 	%s -ports="1234-1236" -vars="Goroutines" -self
 
 For more details and docs, see README: http://github.com/divan/expvarmon
-`, progname, progname, progname, progname)
+`, progname, progname, progname, progname, progname)
 }
diff --git a/self.go b/self.go
index 3d7973e..cee6881 100644
--- a/self.go
+++ b/self.go
@@ -22,7 +22,7 @@ func uptime() interface{} {
 	return int64(uptime)
 }
 
-// startPort defines lower port for bind
+// startPort defines lower port for bind.
 const startPort = 32768
 
 // StartSelfMonitor starts http server on random port and exports expvars.
diff --git a/service.go b/service.go
index b0c6177..a1a4308 100644
--- a/service.go
+++ b/service.go
@@ -8,19 +8,18 @@ import (
 	"github.com/antonholmquist/jason"
 )
 
-var (
-	// uptimeCounter is a variable used for tracking uptime status.
-	// It should be always incrementing and included into default expvar vars.
-	// Could be replaced with something different or made configurable in
-	// the future.
-	uptimeCounter = VarName("memstats.PauseTotalNs").ToSlice()
-)
+// uptimeCounter is a variable used for tracking uptime status.
+// It should be always incrementing and included into default expvar vars.
+// Could be replaced with something different or made configurable in
+// the future.
+var uptimeCounter = VarName("memstats.PauseTotalNs").ToSlice()
 
 // Service represents constantly updating info about single service.
 type Service struct {
-	URL     url.URL
-	Name    string
-	Cmdline string
+	URL           url.URL
+	CustomHeaders map[string]string
+	Name          string
+	Cmdline       string
 
 	stacks map[VarName]*Stack
 
@@ -33,7 +32,7 @@ type Service struct {
 func NewService(url url.URL, vars []VarName) *Service {
 	values := make(map[VarName]*Stack)
 	for _, name := range vars {
-		values[VarName(name)] = NewStack()
+		values[name] = NewStack()
 	}
 
 	return &Service{
@@ -47,7 +46,7 @@ func NewService(url url.URL, vars []VarName) *Service {
 // Update updates Service info from Expvar variable.
 func (s *Service) Update(wg *sync.WaitGroup) {
 	defer wg.Done()
-	expvar, err := FetchExpvar(s.URL)
+	expvar, err := FetchExpvar(s.URL, s.CustomHeaders)
 	// check for restart
 	if s.Err != nil && err == nil {
 		s.Restarted = true
@@ -91,7 +90,7 @@ func (s *Service) Update(wg *sync.WaitGroup) {
 	}
 }
 
-// guessValue attemtps to bruteforce all supported types.
+// guessValue attempts to bruteforce all supported types.
 func guessValue(value *jason.Value) interface{} {
 	if v, err := value.Int64(); err == nil {
 		return v
diff --git a/ui_multi.go b/ui_multi.go
index 3390795..341644d 100644
--- a/ui_multi.go
+++ b/ui_multi.go
@@ -98,7 +98,7 @@ func (t *TermUI) Update(data UIData) {
 	t.Status.Text = fmt.Sprintf("Last update: %v", data.LastTimestamp.Format(time.Stamp))
 
 	// List with service names
-	var services []string
+	services := make([]string, 0, len(data.Services))
 	for _, service := range data.Services {
 		services = append(services, StatusLine(service))
 	}
@@ -128,8 +128,7 @@ func (t *TermUI) Update(data UIData) {
 
 	t.Relayout()
 
-	var widgets []termui.Bufferer
-	widgets = append(widgets, t.Title, t.Status, t.Services, t.Sparkline1)
+	widgets := []termui.Bufferer{t.Title, t.Status, t.Services, t.Sparkline1}
 	for _, list := range t.Lists {
 		widgets = append(widgets, list)
 	}
@@ -200,7 +199,6 @@ func (t *TermUI) Relayout() {
 		t.Sparkline2.Height = h
 		t.Sparkline2.Y = th - h
 	}
-
 }
 
 // Close shuts down UI module.
diff --git a/ui_single.go b/ui_single.go
index 0d5e48a..3af537d 100644
--- a/ui_single.go
+++ b/ui_single.go
@@ -55,7 +55,7 @@ func (t *TermUISingle) Init(data UIData) error {
 		t.Pars[i] = par
 	}
 
-	var sparklines []termui.Sparkline
+	sparklines := make([]termui.Sparkline, 0, len(data.Vars))
 	for _, name := range data.Vars {
 		spl := termui.NewSparkline()
 		spl.Height = 1
@@ -69,7 +69,7 @@ func (t *TermUISingle) Init(data UIData) error {
 		s := termui.NewSparklines(sparklines...)
 		s.Height = 2*len(sparklines) + 2
 		s.Border = true
-		s.BorderLabel = fmt.Sprintf("Monitoring")
+		s.BorderLabel = "Monitoring"
 		return s
 	}()
 
@@ -108,8 +108,7 @@ func (t *TermUISingle) Update(data UIData) {
 
 	t.Relayout()
 
-	var widgets []termui.Bufferer
-	widgets = append(widgets, t.Title, t.Status, t.Sparkline)
+	widgets := []termui.Bufferer{t.Title, t.Status, t.Sparkline}
 	for _, par := range t.Pars {
 		widgets = append(widgets, par)
 	}
diff --git a/utils.go b/utils.go
index 8e4c935..075c455 100644
--- a/utils.go
+++ b/utils.go
@@ -20,13 +20,29 @@ func ParseVars(vars string) ([]VarName, error) {
 	}
 
 	ss := strings.FieldsFunc(vars, func(r rune) bool { return r == ',' })
-	var ret []VarName
+	ret := make([]VarName, 0, len(ss))
 	for _, s := range ss {
 		ret = append(ret, VarName(s))
 	}
 	return ret, nil
 }
 
+func ParseHeaders(headers []string) map[string]string {
+	ret := make(map[string]string, len(headers))
+	for _, header := range headers {
+		tokens := strings.Split(header, ":")
+		if len(tokens) < 2 {
+			continue
+		}
+
+		k := strings.TrimSpace(tokens[0])
+		v := strings.TrimSpace(strings.Join(tokens[1:], ":"))
+
+		ret[k] = v
+	}
+	return ret
+}
+
 // BaseCommand returns cleaned command name from Cmdline array.
 //
 // I.e. "./some.service/binary.name -arg 1 -arg" will be "binary.name".
@@ -41,8 +57,6 @@ func BaseCommand(cmdline []string) string {
 //
 // Note, rawurl shouldn't contain port, as port will be appended.
 func flattenURLs(rawurl string, ports []string) ([]url.URL, error) {
-	var urls []url.URL
-
 	// Add http by default
 	if !strings.HasPrefix(rawurl, "http") {
 		rawurl = fmt.Sprintf("http://%s", rawurl)
@@ -58,6 +72,7 @@ func flattenURLs(rawurl string, ports []string) ([]url.URL, error) {
 	}
 
 	// Create new URL for each port
+	urls := make([]url.URL, 0, len(ports))
 	for _, port := range ports {
 		u := *baseURL
 		u.Host = fmt.Sprintf("%s:%s", u.Host, port)
@@ -66,7 +81,7 @@ func flattenURLs(rawurl string, ports []string) ([]url.URL, error) {
 	return urls, nil
 }
 
-// ParsePorts parses and flattens comma-separated ports/urls into URLs slice
+// ParsePorts parses and flattens comma-separated ports/urls into URLs slice.
 func ParsePorts(s string) ([]url.URL, error) {
 	var urls []url.URL
 	fields := strings.FieldsFunc(s, func(r rune) bool { return r == ',' })
@@ -93,7 +108,7 @@ func ParsePorts(s string) ([]url.URL, error) {
 // for the single port and range of ports to parse.
 //
 // i.e. "http://name:1234-1236/_endpoint" would return "http://name/_endpoint" and
-// "1234-1236"
+// "1234-1236".
 func extractURLAndPorts(s string) (string, string) {
 	var rawurl, ports string
 	parts := strings.Split(s, ":")
@@ -125,14 +140,14 @@ func extractURLAndPorts(s string) (string, string) {
 	return rawurl, ports
 }
 
-// parseRange flattens port ranges, such as "1234-1240,1333"
+// parseRange flattens port ranges, such as "1234-1240,1333".
 func parseRange(s string) ([]string, error) {
 	portsInt, err := ranges.Parse(s)
 	if err != nil {
 		return nil, err
 	}
 
-	var ports []string
+	ports := make([]string, 0, len(portsInt))
 	for _, port := range portsInt {
 		ports = append(ports, fmt.Sprintf("%d", port))
 	}
diff --git a/utils_test.go b/utils_test.go
index f99214f..af458e0 100644
--- a/utils_test.go
+++ b/utils_test.go
@@ -49,6 +49,32 @@ func TestExtractUrlAndPorts(t *testing.T) {
 	}
 }
 
+func TestParseHeaders(t *testing.T) {
+	hdrs := []string{
+		"X-MyCustom-Auth: abcd12345",
+		"Accept-encoding: application/json",
+		"X-Multi-Colon: foo:bar",
+		"X-Spaces-Trimmed:    foobar",
+	}
+
+	parsedHeaders := ParseHeaders(hdrs)
+	if parsedHeaders["X-MyCustom-Auth"] != "abcd12345" {
+		t.Fatalf("Header parsing failed: %v\n", parsedHeaders)
+	}
+
+	if parsedHeaders["Accept-encoding"] != "application/json" {
+		t.Fatalf("Header parsing failed: %v\n", parsedHeaders)
+	}
+
+	if parsedHeaders["X-Multi-Colon"] != "foo:bar" {
+		t.Fatalf("Header parsing failed: %v\n", parsedHeaders)
+	}
+
+	if parsedHeaders["X-Spaces-Trimmed"] != "foobar" {
+		t.Fatalf("Header parsing failed: %v\n", parsedHeaders)
+	}
+}
+
 func TestPorts(t *testing.T) {
 	arg := "1234,1235"
 	ports, err := ParsePorts(arg)
diff --git a/var.go b/var.go
index 8dff7ed..40b707f 100644
--- a/var.go
+++ b/var.go
@@ -13,7 +13,7 @@ import (
 // It has dot-separated format, like "memstats.Alloc",
 // but can be used in different forms, hence it's own type.
 //
-// It also can have optional "kind:" modifier, like "mem:" or "duration:"
+// It also can have optional "kind:" modifier, like "mem:" or "duration:".
 type VarName string
 
 // VarKind specifies special kinds of values, affects formatting.
@@ -35,7 +35,7 @@ const (
 // "slice of strings" is used by Jason library.
 //
 // Example: "memstats.Alloc" => []string{"memstats", "Alloc"}
-// Example: "mem:memstats.Alloc" => []string{"memstats", "Alloc"}
+// Example: "mem:memstats.Alloc" => []string{"memstats", "Alloc"}.
 func (v VarName) ToSlice() []string {
 	start := strings.IndexRune(string(v), ':') + 1
 	slice := DottedFieldsToSliceEscaped(string(v)[start:])
@@ -62,7 +62,7 @@ func (v VarName) Long() string {
 	return string(v)[start:]
 }
 
-// Kind returns kind of variable, based on it's name modifiers ("mem:")
+// Kind returns kind of variable, based on it's name modifiers ("mem:").
 func (v VarName) Kind() VarKind {
 	start := strings.IndexRune(string(v), ':')
 	if start == -1 {
@@ -87,12 +87,12 @@ func Format(v VarValue, kind VarKind) string {
 		if _, ok := v.(int64); !ok {
 			break
 		}
-		return fmt.Sprintf("%s", byten.Size(v.(int64)))
+		return byten.Size(v.(int64))
 	case KindDuration:
 		if _, ok := v.(int64); !ok {
 			break
 		}
-		return fmt.Sprintf("%s", roundDuration(time.Duration(v.(int64))))
+		return roundDuration(time.Duration(v.(int64))).String()
 	}
 
 	if f, ok := v.(float64); ok {
@@ -119,7 +119,7 @@ func roundDuration(d time.Duration) time.Duration {
 		d = -d
 	}
 	if m := d % r; m+m < r {
-		d = d - m
+		d -= m
 	} else {
 		d = d + r - m
 	}
diff --git a/vendor/github.com/nsf/termbox-go/syscalls.go b/vendor/github.com/nsf/termbox-go/syscalls.go
deleted file mode 100644
index 4f52bb9..0000000
--- a/vendor/github.com/nsf/termbox-go/syscalls.go
+++ /dev/null
@@ -1,39 +0,0 @@
-// +build ignore
-
-package termbox
-
-/*
-#include <termios.h>
-#include <sys/ioctl.h>
-*/
-import "C"
-
-type syscall_Termios C.struct_termios
-
-const (
-	syscall_IGNBRK = C.IGNBRK
-	syscall_BRKINT = C.BRKINT
-	syscall_PARMRK = C.PARMRK
-	syscall_ISTRIP = C.ISTRIP
-	syscall_INLCR  = C.INLCR
-	syscall_IGNCR  = C.IGNCR
-	syscall_ICRNL  = C.ICRNL
-	syscall_IXON   = C.IXON
-	syscall_OPOST  = C.OPOST
-	syscall_ECHO   = C.ECHO
-	syscall_ECHONL = C.ECHONL
-	syscall_ICANON = C.ICANON
-	syscall_ISIG   = C.ISIG
-	syscall_IEXTEN = C.IEXTEN
-	syscall_CSIZE  = C.CSIZE
-	syscall_PARENB = C.PARENB
-	syscall_CS8    = C.CS8
-	syscall_VMIN   = C.VMIN
-	syscall_VTIME  = C.VTIME
-
-	// on darwin change these to (on *bsd too?):
-	// C.TIOCGETA
-	// C.TIOCSETA
-	syscall_TCGETS = C.TCGETS
-	syscall_TCSETS = C.TCSETS
-)
diff --git a/vendor/modules.txt b/vendor/modules.txt
index cc660fd..78e97ac 100644
--- a/vendor/modules.txt
+++ b/vendor/modules.txt
@@ -1,14 +1,20 @@
 # github.com/antonholmquist/jason v1.0.0
+## explicit
 github.com/antonholmquist/jason
 # github.com/bsiegert/ranges v0.0.0-20111221115336-19303dc7aa63
+## explicit
 github.com/bsiegert/ranges
 # github.com/gizak/termui v0.0.0-20181228210747-b136f68f55f1
+## explicit
 github.com/gizak/termui
 # github.com/mattn/go-runewidth v0.0.4
+## explicit
 github.com/mattn/go-runewidth
 # github.com/mitchellh/go-wordwrap v1.0.0
+## explicit
 github.com/mitchellh/go-wordwrap
 # github.com/nsf/termbox-go v0.0.0-20180613055208-5c94acc5e6eb
 github.com/nsf/termbox-go
 # github.com/pyk/byten v0.0.0-20140925233358-f847a130bf6d
+## explicit
 github.com/pyk/byten