Closes #411

Signed-off-by: Vishal Rana <vr@labstack.com>

engine/engine.go

@@ -57,6 +57,7 @@ type (
 		Del(string)
 		Set(string, string)
 		Get(string) string
+		Keys() []string
 	}
 
 	// URL defines the interface for HTTP request url.

engine/fasthttp/header.go

@@ -36,6 +36,17 @@ func (h *RequestHeader) Get(key string) string {
 	return string(h.Peek(key))
 }
 
+// Keys implements `engine.Header#Keys` method.
+func (h *RequestHeader) Keys() (keys []string) {
+	keys = make([]string, h.Len())
+	i := 0
+	h.VisitAll(func(k, v []byte) {
+		keys[i] = string(k)
+		i++
+	})
+	return
+}
+
 func (h *RequestHeader) reset(hdr *fasthttp.RequestHeader) {
 	h.RequestHeader = hdr
 }
@@ -61,6 +72,17 @@ func (h *ResponseHeader) Set(key, val string) {
 	h.ResponseHeader.Set(key, val)
 }
 
+// Keys implements `engine.Header#Keys` method.
+func (h *ResponseHeader) Keys() (keys []string) {
+	keys = make([]string, h.Len())
+	i := 0
+	h.VisitAll(func(k, v []byte) {
+		keys[i] = string(k)
+		i++
+	})
+	return
+}
+
 func (h *ResponseHeader) reset(hdr *fasthttp.ResponseHeader) {
 	h.ResponseHeader = hdr
 }

engine/standard/header.go

@@ -29,6 +29,17 @@ func (h *Header) Get(key string) string {
 	return h.Header.Get(key)
 }
 
+// Keys implements `engine.Header#Keys` method.
+func (h *Header) Keys() (keys []string) {
+	keys = make([]string, len(h.Header))
+	i := 0
+	for k := range h.Header {
+		keys[i] = k
+		i++
+	}
+	return
+}
+
 func (h *Header) reset(hdr http.Header) {
 	h.Header = hdr
 }

test/header.go

@@ -24,6 +24,16 @@ func (h *Header) Set(key, val string) {
 	h.header.Set(key, val)
 }
 
+func (h *Header) Keys() (keys []string) {
+	keys = make([]string, len(h.header))
+	i := 0
+	for k := range h.header {
+		keys[i] = k
+		i++
+	}
+	return
+}
+
 func (h *Header) reset(hdr http.Header) {
 	h.header = hdr
 }