FastCGI backend support (#2982)

Co-authored-by: Pierrick Charron <pierrick@adoy.net>

images/fastcgi-helloserver/main.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"net/http/fcgi"
+)
+
+func hello(w http.ResponseWriter, r *http.Request) {
+	keys, ok := r.URL.Query()["name"]
+
+	if !ok || len(keys[0]) < 1 {
+		fmt.Fprintf(w, "Hello world!")
+		return
+	}
+
+	key := keys[0]
+	fmt.Fprintf(w, "Hello "+string(key)+"!")
+}
+
+func main() {
+	http.HandleFunc("/hello", hello)
+
+	l, err := net.Listen("tcp", "0.0.0.0:9000")
+	if err != nil {
+		panic(err)
+	}
+	fcgi.Serve(l, nil)
+}