Add more examples for a custom return Header

Signed-off-by: Alex Ellis <[email protected]>

Author: alexellis

README.md

@@ -88,3 +88,29 @@ func Handle(req handler.Request) (handler.Response, error) {
 ```
 
 The error will be logged to `stderr` and the `body` will be written to the client along with a HTTP 500 status code.
+
+Example reading a header.
+
+```go
+package function
+
+import (
+	"log"
+
+	"github.com/openfaas-incubator/go-function-sdk"
+)
+
+// Handle a function invocation
+func Handle(req handler.Request) (handler.Response, error) {
+	var err error
+
+	log.Println(req.Header) // Check function logs for the request headers
+
+	return handler.Response{
+		Body: []byte("This is the response"),
+		Header: map[string][]string{
+			"X-Served-By": []string{"My Awesome Function"},
+		},
+	}, err
+}
+```

template/golang-http/Dockerfile

@@ -30,7 +30,7 @@ WORKDIR /home/app
 
 COPY --from=0 /go/src/handler/handler    .
 COPY --from=0 /usr/bin/fwatchdog         .
-RUN apk add --no-cache curl
+# RUN apk add --no-cache curl
 USER app
 
 ENV fprocess="./handler"

template/golang-http/main.go

@@ -35,6 +35,12 @@ func makeRequestHandler() func(http.ResponseWriter, *http.Request) {
 
 		result, resultErr := function.Handle(req)
 
+		if result.Header != nil {
+			for k, v := range result.Header {
+				w.Header()[k] = v
+			}
+		}
+
 		if resultErr != nil {
 			log.Print(resultErr)
 			w.WriteHeader(http.StatusInternalServerError)